LIBRARY OF CONGRESS, 



Shelf JEA3 



UNITED STATES OF AMERICA. 



°[ 



Practical Application 



OF THE 



INDICATOR 



WITH REFERENCE TO THE ADJUSTMENT OF VALVE GEAR ON 
ALL STYLES OF ENGINES 



BY 

LEWIS M/ELLIS 



CHICAGO J—VD T~Q ! ~ 



Published by the Author 

25 W. Lake Street 

1894 




3" VI 



COPYRIGHT BY 

LEWIS M. ELLISON, 
1894. 






DEDICATION. 

This work is dedicated, with the highest regard, 
to my friend the working engineer, with the hope 
that it may in some manner benefit and assist him 
in his endeavors to rise to a higher standard of excel- 
lence in his calling. 

The Author. 
January ist, 1894. 



PREFACE. 

While engaged in my work as consulting engineer, 
it has been my fortune to come in contact with a large 
number of working engineers; some more or less ex- 
perienced in the use of the Indicator, others knowing 
practically nothing concerning it. It was gratifying, 
however, to note that whenever called upon to use 
my Indicators, I invariably found an interested spec- 
tator in the engineer, who, in most cases, expressed a 
desire to learn their use. In some cases, where de- 
sired I have given personal instructions, but in many 
cases the engineer could not afford such an expensive 
method of learning. To these, I recommended va- 
rious works on the subject, but found the very general 
complaint that most of the works on the Indicator 
now published are not sufficiently definite for the be- 
ginner. These circumstances, together with the fact 
that I have personally felt the want of more practical 
information on the subject than is contained in exist- 
ing books, have, to a great extent, induced me to 
prepare this volume; and it has been my aim to cover 
the ground as thoroughly as possible, and produce a 
work which will meet the requirements of the beginner 
as well as the experienced engineer. As so many of 
our engineers have not had the benefit of even a com- 
mon school education, I have endeavored to use only 
such wording as would be readily understood by all, 
and avoid all intricate formulas which tend to confuse 

5 



6 # Preface. 

and mislead the reader. The importance of the Indi- 
cator is now so generally recognized that the time is 
rapidly approaching when no engineer will be consid- 
ered competent unless he is proficient in the use of 
the Indicator; and if this effort on my part shall have 
made the subject plainer to some, or in any degree 
assisted those who desire to better their condition, I 
shall feel amply repaid for the time and labor expended 
in the preparation of this work. 

Lewis M. Ellison. 
Chicago, Jan. i, 1894. 



INTRODUCTION. 

The steam engine indicator is an attachment to 
the steam engine, which has been too long neglected. 
In fact, only a few years have elapsed since it was 
practically unknown to the average working engineer. 
However, questions were continually coming up which 
called for a frequent resort to its use, until now, in 
the hands of a skillful engineer, it is a very important 
factor, in the running of the steam plant. The first 
indicator, I believe, was invented by James Watt and 
was a very crude affair, adapted for use only on en- 
gines of low pressure and running at slow speeds. It 
would be wholly unfit for use on the high pressure and 
high speed engines of the present day. Meantime, 
the changes in the styles of engines necessitated 
changes and improvements, and the makers of indi- 
cators have endeavored to keep pace with the times; 
and there is no doubt that the American indicators of 
•to-day, for simplicity, accuracy and durability, far 
surpasses any like devices in the world. The benefits 
derived from the use of the indicator becoming more 
and more apparent, have greatly increased the de- 
mand, and recently there have been put upon the 
market several new makes and styles which are duly 
appreciated and which show the enterprise and me- 
chanical skill of the maker. Nevertheless, we regret 
that they have not aimed to produce a more reliable 
and accurate instrument rather than one where relia- 

7 



8 Introduction . 

bility is sacrificed to price. While some of the older 
makes of indicators are reasonably correct, the ma- 
jority of the recent makes are practically worthless 
when accuracy is desired and few of them will give 
two readings alike. It is to be hoped that the day 
will soon pass when such instruments will be recog- 
nized by intelligent engineers. I wish to state here 
that I have no connection or interest, financial or 
otherwise, with any indicator or attachment, steam 
engine or steam appliance, and wherever comparisons 
are made they are used simply as facts for the benefit 
of the readers and without any preference or prejudice 
on my part. With few exceptions the diagrams used 
in this work were taken by myself in actual practice 
and are engraved as nearly as possible as taken, full 
size and contain all the peculiarities of the original 
diagram. The demonstrations are put in the simplest 
language, so that all can fully understand them with- 
out reference to the higher mathematics, and some of 
them have never before appeared in print and will no 
doubt prove interesting. 



PRACTICAL 

APPLICATION OF THE INDICATOR. 



CHAPTER I. 



THE INDICATOR. 



The indicator is an instrument for registering on 
paper the varying steam pressure on the piston of an 
engine during both the forward and return stroke. 
It consists, essentially, of a small steam cylinder, hav- 
ing on its axis a small drum upon which the paper is 
rolled. This drum revolves backward and foiward 
by a motion derived from the crosshead of the engine. 
The cylinder is provided with a piston whose motion 
is resisted by a spiral spring. Steam is admitted be- 
neath this piston, and as it is at a greater or less 
pressure, so is the spring more or less compressed 
and the piston rises and falls accordingly. The 
motion of the piston is conveyed by a series of 
levers to a pencil which is pressed against the paper 
on the drum. Before using the indicator clean the 
bearing surfaces of the cylinder and piston and lubri- 
cate them with the best cylinder oil that is clean and 
does not stick or gum. Use refined porpoise jaw oil 
on all the other bearings. On tests of long duration, 
the piston should be taken out and together with the 

9 



10 Practical Application of the Indicator 

cylinder should be cleaned and oiled frequently as 
necessary. The central bearing upon which the 
drum rotates, is subject to much wear and should be 
frequently cleaned and oiled. After using the instru- 
ment, thoroughly clean and oil it, being especially 
particular in regard to the springs as a very slight 
rust impairs their accuracy. It is of importance that 
an indicator be kept in good order and to determine 
that it is properly adjusted and constructed, the 
following is a good method. With the indicator 
in a vertical position and without the spring (with 
piston attached) ; raise the pencil motion to its highest 
position and when released it should drop with free- 
dom from friction to its lowest position. The piston, 
cylinder and oil must be warm, otherwise the piston is 
apt to stick . As a further test, again raise the pencil 
motion to its highest position and cover the hole 
through which steam is admitted to the indicator with 
the thumb when the pencil should sink at a slow and 
uniform rate through the whole range of its motion. 
Should there be a suspicion of a catch from any posi- 
tion within this range, detach the piston from the 
pencil motion and try the pencil motion and piston 
separately. If both are in good order the fault lies 
where the piston is attached to the pencil motion. A 
piston which is too free may occasion serious defects 
from leakage, especially in condensing engines. The 
pencil motion should be parallel to the drum surface 
and the drum be perfectly round and properly cen- 
tered. By adjusting the pencil stop so that only a 
ray of light can be seen between the pencil point and 
the drum surface, the piston is moved upward (with a 



Practical Application of the Indicator. 



11 



lead pencil) and the pencil point should be carefully 
watched to see that it keeps the same distance from 
the drum surface. With the pencil, both in the high- 
est and lowest position, rotate the drum through its 
whole range by drawing out the cord and again watch 




the pencil point. Then apply the paper and allow 
the pencil to touch the paper and repeat the operation 
by forming two horizontal lines and one vertical 
line. 



12 



Practical Application of the Indicator. 



If the reduction is correct, the lines drawn will be 
straight throughout th,eir whole length and at right 
angles to each other which may be proven with the 
angles as shown in Fig. I. Those made of celluloid 
are preferred. To determine that all joints are with- 
out play, insert a spring of high tension and carefully 
feel at the end of the pencil bar. In case two indi- 
cators are used they should be either both right or 
both left hand. 

PAPER. 

The paper used with the indicator should be of 
good quality, having a smooth surface and capable of 
receiving an impression with the lightest possible 
pressure of the pencil against the paper. Paper hav- 
ing a glossy surface should be avoided. The paper 
should reach to the top of the drum and about one 
inch longer than the circumference of the drum. 
Printed blanks containing spaces for recording various 
observations for future references are preferable. 
Those used by the writer are prepared for the partic- 
ular test on which they are to be used. Those shown 
in Fig. 2, are shown one-half size and arranged for a 

Lewis M. Ellison, Consulting Engineer, 25 W. Lake St., Chicago. 

DIAGRAM FROM ENGINE AT 



OIAM OF CYLINDER 

OIAM OF PISTON BOD 

DIAM OF STEAM PIPE 

OIAM OF EXHAUST PIPE. 



. PER-CENT.CF CLEARANCE, 

. STROKE IN INCHES 

. REV.PER MIN. 

. SCALE OF SPRINQ 



BOILER PRESSURE.- 
INITIAL PRESSUaE._ 

BACK.PRESSURE. 

MEAN EFFECTIVE PRESSURE.. 



. VAC.PER GAUGE, INCHES 

. BAROMETEft.REAUS 

.TEMP.HOT WELL 

INDICATE DMORSE POWEK_ 



u, a D o 

Sill 



Fro 2. 



Practical Application of the Indicator. 13 

drum two inches in diameter, will usually be sufficient 
for the engineer. Remember, that without all neces- 
sary data the diagram is worthless except as an indi- 
cation of the valve setting. In getting the correct 
data in making indicator tests remember the golden 
rule is, never take anyone's word for anything. But 
note these observations yourself which must be under- 
taken with a degree of precision, as many a man's 
evidence in court has been disallowed for want of 
sufficient and reliable data. 

The paper should be placed so that the clips hold 
it on the drum as smooth as a glove. To accomplish 
this, close to the clips, with the thumb and forefinger 
pinch the ends of the paper together. Never attempt 
this operation by pulling on the ends of the paper, as 
it springs the clips outward which in turn sets the 
paper away from the drum. 

PENCIL. 

Use hard lead and of good quality such as usually 
accompanies the indicator. It should be sharpened 
with fine sandpaper to a smooth point, as fine lines 
are preferable for their distinction. The lead should 
project through the socket as little as possible, so as 
to avoid undue twisting of the pencil bar. The pres- 
sure of the pencil on the paper should be just suffi- 
cient to make a legible mark, a greater pressure only 
creates undue friction. The friction of the pencil 
tends to lessen oscillations, but at the same time it 
falsifies the diagram. A more satisfactory result can 
be obtained by using a metallic point in place of the 
pencil and it, like the lead, should be as light as pos- 



14 Practical Application of the Indicator. 

sible, for, its weight acting at the end of the lever 
where the velocity of motion is at its maximum will 
tend to increase oscillations. It should be sharpened 
to a fine point, rounded off on the end so as not to 
tear the paper while at the same time make a fine 
but distinct line. The metallic cards are chemically 
prepared for the metallic points. 

SPRINGS. 

In order to obtain a correct diagram, the height 
of the pencil (caused by the compression of the spring) 
must exactly represent in pounds pressure per square 
inch the pressure on the piston of the engine at any 
point of the stroke and the velocity of the drum must 
at all times bear a constant ratio to that of the piston. 

In selecting a spring to suit different conditions, as 
to steam pressure, speed, etc., the aim should be to 
obtain a diagram about two inches high on slow speed 
engines and about one and one-fourth inches or less 
on high speed. This is accomplished by using a 
spring that is numbered one-half the highest pressure. 
Thus, if a 40 spring is used, forty pounds pressure per 
square inch will raise the pencil one inch, and eighty 
pounds two inches and so on for other pressures. The 
spring is the measuring factor of the indicator and the 
most vital part of the instrument. Indicator springs 
give to-day, as a rule, more power on an engine than 
they would give if the springs were correct. For 
tests of importance the scale of deflection should be 
verified before and after each test. The rule for 
giving the maximum pressure to which each spring is 
subjected varies with different makes of indicators; 
therefore it is not given here. 



CHAPTER II. 

APPLICATION OF THE INDICATOR." 

The application of the indicator to an engine is a 
scientific experiment and should be undertaken with a 
degree of care and precaution against error, as the 
value of the diagram depends on its correctness. The 
value of the indicator is now so generally recognized 
that every concern which pretends to manufacture an 
engine makes provision for its application. When no 
provision for its application has been made, the cylin- 
der must be drilled and tapped for not less than one- 
half inch pipe thread, in the side where the pantograph 
reducing motion is used, but usually on top for high 
speed and in such position in the clearance space that 
the holes are not the least covered over by the piston 
at the end of its travels. Should the clearance space 
be too small to allow for this, access may be had by 
chipping a channel in the cylinder head from the 
tapped hole out into the clearance space. In drilling, 
the piston should be taken out and the cylinder cleaned 
from chips and cuttings. The indicator should be 
connected as directly as possible to the cylinder. For 
the reason that it requires a difference in the pressure 
in order that the steam can flow from the engine cyl- 
inder into the indicator, thus causing a loss of pressure 
in the steam line and an increase of pressure in the 
expansion curve and with long connections, such as 
the use of side pipes connected at the middle with a 

15 



16 Practical Application of the Indicator. 

three-way cock as shown in Fig. 3, or still worse 
a T with an angle valve at each end which is one 




Fig. 3. 



of the most objectionable forms, the results will show 
up later in the indicator than when it took place in- 
side of the steam engine cylinder. 

The cock should be screwed into the cylinder 
itself. When the cylinder is tapped upon the side 
this will bring the instruments horizontal. Where 
nipples and elbows are used to bring the indicator into 
a vertical position, the ends of the nipples must be 
reamed out, as the burr made in cutting it if not 
reamed wire-draws the steam. Use no leads or paints 
in connecting, it is not necessary and they are liable to 
get into the instrument. When, however, a single 
indicator is to be used upon both ends of the cylinder, 
and where engines are constantly changing their load, 
the three-way cock is sometimes used to equalize the 
work between the two ends of the cylinder. The 
most proper arrangement is to have an instrument 
upon each end of the cylinder from which simulta- 
neous diagrams may be taken. 



Practical Application of the Indicator. 



17 



REDUCING MOTION. 

Whenever the stroke of the engine is greater than 
the length of the diagram desired, some means must 
be provided to reproduce upon a reduced scale a per- 
fect duplicate of the piston movement, many devices 
in use fail to do so, and the diagrams taken with them 
are incorrect. The pantograph, as shown in Fig. 4, 
is a correct reducing motion, and various lengths of 




Fig. 4. 

diagrams may be had by changing the position of the 
cross-bar D, moving it toward the end pivot A for 
longer diagrams, and toward the end pivot B for 
shorter ones. The cord pin C must be in line with 
the end pivots A and B. The cord pin is grooved for 
the application of the cord, but its diameter is usually 
so great that it tends to throw the cord. To prevent 
this it should be regrooved to a diameter of about 
one-eighth of an inch. The joints can readily be 



18 



Practical Applicatio?i of the Indicator, 



tightened when they are too loose, by upsetting the 
rivet heads. When not in use, the whole apparatus 
should be kept in a bath of oil which at the same 
time lubricates the joints. The arrangement for sup- 




Fig. 5. 

porting and attaching the pantograph differs as the 
ingenuity of the operator may suggest. 

The simple device as shown in Fig. 5 is con- 
structed of half-inch nipples and fittings. A is 
screwed into the side of the crosshead, the oil cup 
being removed and placed in the tee. The length of 
A should be about four inches so as to prevent the 
corners, E. E. of the pantograph from coming in con- 



Practical Application of the Indicator. 



19 



tact with the crosshead. The height of B should be 
about four inches so as to bring the pantograph to the 




Fig. 6. 



proper level. B can be turned at any angle, as shown 
in Fig. 6, to suit various sizes of engines. A wooden 



4- i>- -fr-H / 




&~ 4" ■$- 



X 



Fig. 7. 



plug is driven into C and bored out to receive the end 
pivot A of the pantograph. 

On crossheads similar in style to Fig. 7, A can be 
made of round iron, flattened and slotted near the 



20 



Practical Application of the Indicator. 



end as shown in Fig. 8 when it will fit any bolt 
and can be clamped fast to one of the bolts 
uf the crosshead. Fig. 9 shows the arrangement 
for supporting the end pivot B of the pantograph. 
This device is constructed of about 4 feet of | inch 
gas pipe which can be made up with couplings 
so that it can be disconnected into parts, there- 
by rendering it convenient in moving from place 




/ 



to place. The clamps A and B are made of 
tough wood. A is about 1^ inch thick x 1 } 2 wide x 6 
inches long and slotted at the end, and with a bolt can 
be made fast any place on the pipe so as to get the 
correct height for the pantograph. A hole is made 
near the other end for the end pivot B of the panto- 
graph. The floor plate is made fast to the floor with 
screws. One brace is parallel with the engine and 
made fast to the floor and the short clamp B and an- 
other brace at right angles made fast near the top 



Practical Application of the Indicator. 



21 



with a similar clamp or into a wooden plug which is 
driven into the top of the pipe while the other end of 
the brace is usually fastened to the wall or over on to 
the engine frame. It is immaterial whether the sta- 
tionary end of the pantograph be placed in the center 
of motion or not so far as correctness goes and makes 
no difference whether the pantograph is set horizon- 




Fig. 9. 



tally, perpendicularly or oblique so long as the corners 
E. E. of the pantograph will clear. 

Some writers claim that the stationary end of the 
pantograph must be precisely in the center of motion, 
which is a mistaken idea, and has caused many engi- 
neers to measure with precaution against error to lo- 
cate this point correctly. Owing to the complicated 
construction of the pantograph, it cannot be used on 
high speed engines, and is frequently replaced by a 



22 



Practical Application of the Indicator. 



light wooden pendulum pivoted to a fixed support 
usually -a | inch gas pipe screwed into the engine 
guide as shown in Fig. 10 and fitted at its lowest ex- 
tremity with a pin which is carried by a slot made fast 



4 



I.:: 





Fig. 10. 

to the crosshead as shown in Fig. n. The length of 
the pendulum should be about one and a half times 
the stroke of the engine. The cord is looped or hook- 
ed on a pin which must be in the center line of the 
pendulum and on a point on the pendulum to corre- 
spond with the length of diagram, and the cord must 



Practical Application of the Indicator. 



23 



be precisely at right angles to the pendulum when it 
is in the middle of the stroke. The point of support 
must be precisely in the center of motion and must 
not vary to the edge of a knife blade otherwise it will 





Fig. 11. 



Fig. 12. 



distort the diagram and the results will appear un- 
equal if they really are equal. 

When a link is used in connection with the pen- 
dulum as shown in Fig. 12, the link should be about 
one-half the stroke. The pendulum should be ar- 
ranged so that the link will incline as much below the 



24 Practical Application of the Indicator. 

path of the crosshead when in the middle of the stroke 
as it inclines above the path when at the end of its 
travel. The fixed support of the pendulum will then 
be at a point as far from the support of the slotted 
pendulum as the distance from A to B. Frequently 
provisions are made near one end on the guide for 
making the support fast, and in order to have the 
same inclination, the relative length of the pendulum 
and link must be such that at midstroke the pendulum 
is perpendicular, when it is a horizontal engine, and 
at right angles to the plane in which the crosshead 
moves. 

While both of the motions last mentioned are fre- 
quently used neither of them are correct. The use 
of a segment of a pulley, sometimes called the 
Brumbo pulley, introduces rather than eliminates an 
error. The correctness in the reduction of any re- 
ducing motion can readily be determined by placing 
the engine so that the crosshead is at either end of 
its travel with reducing motion and indicator properly 
attached. First, draw a horizontal line by pulling 
out the cord and without the spring make a vertical 
mark upon the card by raising the pencil and with the 
engine in this position make a mark on the crosshead 
and guide. Space off as many marks on the guide as 
the length of stroke is in inches, move the engine so 
that the mark on the crosshead coincides with each 
mark on the guide, and at each movement make a 
corresponding mark on the card. If the lines are 
equally spaced, as shown in Fig. 13, the principle of 
the reduction is correct, while its practicability when 
at full speed may be radically distorted. If so, it is 



Practical Application of the Indicator. 



25 



due to several causes, but principally vibration of tne 
reducing motion or indicator. Frequently cord stretch- 
ing or throw of the indicator drum will cause a dis- 
tortion of the diagram which can be tested by first 
taking the atmospheric line while the engine is run- 



Fig. 13. 



ning slow, then move the card upward about 1-16 of 
an inch and take another line when the engine is at 
full speed. If there is a difference in the length of 
the lines, distortion is generally due to one or more 
of these causes. 



CHAPTER III. 

CORD. 

The movement of the paper drum is derived from 
a closely braided hemp or metallic cord, all of which 
are more or less elastic. The result of the elasticity 
"in the hemp cord" is that at the end of the stroke, 
the cord having to overcome the throw of the drum, 
the tension of the drum spring stretches the cord 
more or less at the commencement of the stroke. 
The drum loses a part of its movement at the com- 
mencement of the stroke, but gradually regains its 
curtailment at the end of the stroke by giving the 
drum a throw, thereby affecting a motion proportion- 
ate to that of the piston movement. The result of 
the elasticity in the metallic cord is that the drum re- 
tains its proportional movement to the end of the 
stroke when the throw of the drum produces an 
elongation of the diagram. The hemp cord is there- 
fore the most efficient to eliminate this distortion 
When any great length has to be used, it is well to 
partly substitute metallic wire for hemp cord. The 
braided cord is supplied by dealers in the instruments; 
but before using, it should remain suspended for at 
least one day with a heavy weight at its lowest end 
to take out any undue stretch which it may contain, 
after which it should be treated with a light coat of 
beeswax, when it will not be easily affected by moist- 
ure and will longer retain its proper condition. The 

26 



Practical Application of the Indicator 27 

cord should be looped over the cord-pin on the re- 
ducing motion which permits the pin to turn easily 
within it, and should be hooked and unhooked at that 
point. Nearly every engineer at first expects a diffi- 
culty in hooking and unhooking the cord on high 
speed engines, which is merely supposition. The 
writer has taken diagrams on some of the highest 
speed engines built and never experienced the slight- 
est difficulty. When a hook is used it must be light 
and hooked upon the cord-pin itself, or as near the 
instrument as possible. The device frequently used 
for adjusting the length of the loop and cord, and 
usually made of a small piece of stiff mefalin which 
are drilled four holes for the cord to pass through, 
thereby forming the loop, is a device about as worth- 
less as can be made, and when it is on the middle of 
the line, together with the heavy hook now so com- 
mon in use, it is in its most objectionable form, and 
will cause the cord to whip. The length of the dia- 
gram on slow speed engines should be about four 
inches and about two inches high, as large diagrams 
will show up the defects to greater advantage. The 
length of diagram desired can easily be determined 
by taking hold of the cord in one hand and allow it 
to pass over a rule held in the other hand with the 
engine running slow. When a hook and loop are 
used, the length of the cord is adjusted so that the 
hook clears the loop about one inch at the end of the 
stroke, and since a drum two inches in diameter un- 
winds the cord about six inches, this will give a clear- 
ance of one inch to the drum at each end of the 
stroke, when the diagram will come in the center of 



28 Practical Application of the Indicator. 

the card. The proper tension of the drum spring is 
of importance. If too little tension it will cause the 
drum to throw past at the end of the stroke when the 
cord will be constantly whipping, and if the tension 
is too great the drum loses a part of its stroke, a mat- 
ter which can be easily tested. With the engine run- 
ning slow and with a tension on the drum spring, so 
that it neither causes the cord to stretch nor the drum 
to throw, take the atmospheric line, move the card 
up about I- 1 6 of an inch, put the engine up to speed 
and readjust the drum spring to the supposed proper 
tension and take another atmospheric line. If the 
last line is the longest the tension of the drum spring 
is too little, which caused the drum to throw, and if 
shorter the tension is too great. 

It is desirable to avoid the use of leading pulleys 
as shown in Fig. 12; however, when it becomes neces- 
sary in order to lead the cord off parallel with the 
guides, a leading pulley must be used and from this 
the cord may be carried in any direction. For high 
speed engines the length of the diagram should be 
about .2 to 2\ inches and from 1 to ij inches high 
and it is desirable to use a lighter and smaller drum 
on high speed engines. 

HOW TO ATTACH THE INDICATOR AND TAKE THE 
DIAGRAMS. 

Before attaching the indicators, steam should be 
blown through the cocks so as to remove any grit 
which may be in the connections. Fig. 14 shows the 
indicators properly attached to a Corliss engine, for 
taking steam pipe and cylinder diagrams, with the 



Practical Application of the Indicator. 



29 




Fig. 14. 



SO Practical Application of the Indicator. 

pantograph reducing motion and its attachments com- 
plete. Before taking a diagram, steam should be ad- 
mitted into the indicators during several revolutions 
of the engine and when dry steam blows through the 
relief, apply the pencil during one revolution, but 
where the load is constantly changing and when the 
power is to be computed from the diagrams, the pen- 
cil should be applied during as many revolutions as is 
necessary in order to obtain both the lightest and 
heaviest load, from which the average horse power 
may be ascertained. After taking the diagrams, steam 
should be shut off from the indicators and the atmos- 
pheric line should be taken immediately, before the 
spring contracts, as the indicator piston rod and 
spring expand when in contact with steam and con- 
tract when steam is shut off, due to the difference in 
temperature. The result is that the expansion of the 
piston rod raises the pencil and the expansion of the 
spring lowers it, and when steam is shut off, the con- 
traction of the piston rod and spring affects the pen- 
cil vice versa. Now if the expansion and contraction 
of the rod and spring were the same, one would bal- 
ance the other, but they are not the same, conse- 
quently, the atmospheric line should be taken imme- 
diately after the diagram, so that the conditions in 
both rod and spring may be as nearly the same as 
possible. After unhooking the line, let the indicator 
drum revolve gently back against the stop. 

TESTING STEAM GAUGE WITH THE INDICATOR. 

To determine the loss of pressure between the 
boiler and engine, the steam gauge and indicator 



Practical Application of the Indicator. 



31 



must agree, or if any variation, it should be known. 
Fig. 1 5 shows the indicator and steam gauge properly 
connected for making this test. They must be attached 
where there is no fluctuation in pressure. A conven- 




Fig. 15. 

ient place is above the throttle valve when steam is 
shut off from the engine. To take this diagram turn 
steam on the gauge and indicator and when they are 
well heated up take the steam pressure line by draw- 
ing out the cord and at the same time note the read- 



32 Practical Application of the Indicator. 

ing of the steam gauge. Shut off steam from the in- 
dicator and take the atmospheric line. Fig. 16 shows 
the diagram taken with 40 spring. Measure on the 
scale of the spring from the atmospheric line to the 
steam pressure line which is 80 pounds and if the 



Fig. 1( 



gauge registers the same they agree for this pressure, 
while for other pressures they may disagree, as 
an indicator spring and a steam gauge vary more at 
some pressures than at others. If the gauge registers 
the greater pressure it is light, and if less it is heavy, 
providing the indicator spring is correct. 



CHAPTER IV. 

DIAGRAM ANALYSIS. 

An indicator diagram is the result of two move- 
ments, namely, a horizontal movement of the paper 
and a vertical movement of the pencil, and therefore, 
represents by its length, the stroke of the engine on a 
reduced scale; and by its height, at any point, the 
pressure on the piston at a corresponding point in the 
stroke. A single diagram shows the pressure acting 
on one side of the piston during both the forward and 
return stroke. To show the corresponding pressure 
on the other side it is necessary to take another dia- 
gram from the other end of the cylinder. 

The following definitions have been given to the 
different parts of the diagram proper and to lines 
added, as required for purpose of analysis. Fig. 17 
shows the general features of a well formed indicator 
diagram from a Corliss non-condensing engine, the 
attainment of which should be the aim in setting the 
valves of an engine. Line A B is the admission line 
which indicates lead only , and steam should not be 
admitted into the cylinder until the piston has com- 
pleted its stroke. But before the piston moves away, 
the steam valve should open and admit the pressure 
so as to erect the admission line perpendicular to the 
atmospheric line. This can be proven by placing one 
side of a right angle, parallel with the atmospheric 
line and the other extending a trifle beyond the ad- 
3 33 



34 



Practical Application of the Indicator. 



mission line. Then draw line I. If the admission line 
is parallel with this line, the admission is perfect. If 




* 



<b &* 



the admission line leans inward, the admission is too 
late and causes loss of power and economy. If the ad- 
mission line leans outward, the admission is too early, 



Practical Application of the Indicator. 35 

which by all means must be avoided, unless it is nec- 
essary in order to obtain the necessary cushion when 
the cushion from the exhaust steam is insufficient, 
which frequently happens with overloaded engines or 
condensing engines, as it forms a counter motion on 
the piston which also is a loss of power and economy, 
and were it not for the motion of the fly wheel in 
assisting to bring the crank beyond the center, the 
engine would stop. If there is any choice between a 
too early and a too late admission it is better to have 
it too late. Line B C is the steam line which indi- 
cates the stroke of the piston to the point of cut-off. 
An engine that can maintain the nearest to a straight 
-steam line is the most efficient. 

The initial pressure is the first pressure realized in 
the cylinder at the commencement of the stroke, and 
is measured on the scale of the spring from the atmos- 
pheric line to the highest true point at the commence- 
ment of the steam line. The initial pressure should 
maintain to the point of cut-off and approach the 
boiler pressure as nearly as possible, and if the boiler 
and engine are a reasonable distance apart and all 
steam passages are ample, there should not be a 
greater loss of pressure than from 2 to 3 pounds. A 
greater loss is principally due to insufficient area 
through the steam pipe, steam chest, and ports (which 
can be located with the indicator) and generally fol- 
lows with rapid falling of the steam line which is 
sometimes called wire-drawing. It is also due to 
condensation caused by too many expansions. J J is 
the boiler pressure line and is located by measurement 
on the scale of the spring at such a distance above 



36 Practical Application of the I?idicator. 

the atmospheric line as to represent the boiler pres- 
sure at the time the diagram was taken, and the loss 
of pressure between the boiler and engine is measured 
from the steam line to the boiler pressure line. C is 
the point of cut-off where the steam valve closes auto- 
matically by action of the governor, either by changes 
of pressure of steam or changes of load. When the 
valve closes it should be quick in its action so as to 
form the point C as sharp as possible. A valve that 
is slow in closing reduces the pressure at this point 
which is a loss of economy. After the valve has 
closed there should be no leakage of steam in the 
valve, as this leakage is a partial loss of economy on 
the admission side of the piston and a total loss on 
the exhausting side except during compression. The 
leakage of valves — when it exists — will be the greatest 
immediately after the valve closes, when the difference 
of pressure in the cylinder and the steam chest is the 
least, as the valve is not held so firm to the seat. C 
D is the expansion curve comparing it with what is 
known as Mariotte's law, according to which, its vol- 
ume and pressure are inversely proportional to each 
other, and for elementary sake will assume that an 
engine has no clearance and that steam follows this 
law. And if ioo pounds absolute pressure be ad- 
mitted into the cylinder of an engine and cut-off at \ 
stroke, when the piston has moved to \ stroke, the 
volume will be doubled and if there be no loss in pres- 
sure from condensation or gain from re-evaporation, 
leakage of piston, valves, etc., the pressure would be 50 
pounds absolute; when the piston has completed its 
stroke, the volume will again be doubled from what it 



Practical Application of the Indicator. 37 

was at i stroke and the pressure will be 25 pounds abso- 
lute, and so on for other pressures and volumes. But 
steam does not follow this law, as it is a known fact that 
it falls in temperature during expansion and rises during 
compression and this change of temperature augments 
the change of pressure so that as before assumed, 100 
pounds absolute pressure be cut-off at \ stroke instead 
of falling 50 pounds at \ stroke will fall to a trifle 
below 48 pounds. The absolute pressure is the 
gauge pressure plus the atmospheric pressure and 
is the basis for all calculations for expansion and 
compression. 

The object of expanding steam is to obtain econ- 
omy and therefore it should be expanded to its great- 
est reasonable extent. If steam is expanded down to 
the atmospheric pressure so that all its force has been 
utilized in doing work it will lower the temperature of 
the cylinder walls, etc. , to such a degree that it will 
result in too great condensation of the entering steam 
and will be a loss rather than a gain, and if released 
at too high pressure, when it could yet do useful work, 
will also result in loss of economy. The most suit- 
able release pressure depends upon several conditions 
and should be in accordance with the initial pressure 
so as to effect an economical range of temperature in 
the cylinder. 

D is the point of exhaust opening and should be 
as near the end of the stroke as possible. The ex- 
haust valve should open quickly so as to release 
the pressure and bring it down where it belongs be- 
fore the piston starts to return. 

The release pressure is measured from the atmos- 



38 Practical Application of the Indicator. 

pheric line to the point D, and represents the pressure 
at which steam is released. The terminal pressure is 
the pressure at the end of the stroke. EF is the 
back pressure line and is measured from the back 
pressure line to the atmospheric line. If the exhaust 
passages are ample there should be no more back 
pressure than a fraction of a pound due to friction in 
the passages, etc., unless the exhaust be utilized for 
other purposes than that of heating the feed water, 
because back pressure represents power and fuel 
thrown away as it requires just that much more pres- 
sure on the admission side of the piston to overcome 
it and if carried to extreme, the engine would stop. 
Excessive back pressure is due principally to insuffi- 
cient area in the heater, exhaust pipe, and ports and 
can be located with the indicator. Many exhaust 
pipes have not sufficient size drip to allow the water 
of condensation to properly escape without partly 
filling the pipe, thereby reducing its size and causing 
back pressure. I have found some that have no drip 
which is still worse. If there were no back pressure 
the back pressure line would merge into the atmos- 
pheric line. 

F A is the compression curve and is formed by 
closing the exhaust valve at the point F before the 
piston completes the stroke thereby imprisoning the 
exhaust steam which is compressed as the piston com- 
pletes the stroke. The compression is measured from 
the atmospheric line to the point A which effects an 
equal amount of cushion per square inch on the piston 
only at the time when the pressure on the other side 
of the piston is equal to that of the atmospheric which 



Practical Application of the Indicator. 39 

forms an elastic cushion to stop the piston and its 
reciprocating parts at the end of the stroke. 

Engines running from 60 to 200 revolutions per 
minute may require from about 10 to 45 pounds 
cushion. The amount of cushion per square inch on 
the piston depends principally on the weight of these 
parts and the speed of the engine, and no more 
cushion should be given than is required to accomplish 
this result, as a greater amount has the same defect 
as too early admission. It takes an additional amount 
of steam on the admission side of the piston to form 
compression; but if there were no loss of heat from 
condensation during compression and expansion, and 
the steam be expanded to the same pressure as that 
when the exhaust valves closed, there would be no 
loss from compression. Condensation, however, ex- 
ists which causes loss of economy from compression; 
yet if the clearance space be filled with live steam, 
whose temperature is greater than that of the cylinder 
walls, etc., it would also result in loss of economy 
from condensation; therefore to obtain the greatest 
economy direct from compression it should be at a 
temperature that does not exceed the temperature of 
the cylinder walls, etc. Cylinder condensation has 
led some engine builders, as well as engineers, to be- 
lieve that a steam jacketed cylinder is more econom- 
ical than an unjacketed one, but this is a mistaken 
idea and whenever tests have favored the steam jack- 
eted cylinder, the conditions have been unfavorable 
for the unjacketed cylinder. 

G G is the atmospheric line, from which all pres- 
sure above and vacuum below must be measured. 



40 Practical Apphcatio?i of the Indicator. 

H H is the vacuum line and is located by measure- 
ment on the scale of the spring at such a distance 
below the atmospheric line as to represent the atmos- 
pheric pressure in pounds per square inch at the time 
and place; but the pressure is constantly changing, at 
sea level the average being 29.922 inches, or about 
14.7 pounds and for higher altitudes, correspondingly 
less. The reading of the barometer in inches, multi- 
plied by .49 will give the pressure in pounds. 



CHAPTER V. 

CUSHION. 

The cushion is the highest unbalanced pressure 
per square inch on the piston at the end of the stroke, 
and serves to stop the piston and the reciprocating 
parts at the end of the stroke, so as to relieve the 
connections from undue strain. 

Suppose it is desired to determine the cushion per 
square inch on the piston of Fig. 18. H represents 
the head end and C the crank end of a Corliss engine. 
The compression on the head end is 20 pounds, 
which is sufficient cushion per square inch on the 
piston for engines running at about the speed of the 
average Corliss engine; but the pressure on the 
other side of the piston when it comes to a standstill 
must be deducted, and should be measured on the 
crank end diagram, at such point as shown by the 
dotted line, which is 10 pounds. Therefore, the 
cushion is only 10 pounds and not 20 pounds, as 
shown by the compression. This is a mistake often 
made by some of our best engineers, as well as some of 
the so-called indicator experts. When this pressure 
is the same as the compression then the pressure is 
equal on both sides of the piston and there is no 
cushion. This frequently happens when the engine 
is overloaded. When engines are taking steam 
nearly full stroke, it will cause them to pound, not 
because they are working hard, as is so often sur- 

41 



42 



Practical Application of the Indicator. 



mised by some engineers, but from the fact that this 
pressure may be even greater than the compression, 
when the tendency is to send the piston still further, 
were it possible to do so. This is an important fac- 
tor which has been too long ignored, and has caused 




Fig. 18 — Scale op Spuing 40. 

many engines to run noisy when it could be easily 
prevented. The cushion on the crank end is de- 
termined in like manner, by measuring the compres- 
sion of the crank end, from which deduct the 
pressure of the head end at a point as shown by the 
dotted line. If the exhaust valve rods be lengthened, 



Practical Application of the Indicator. 43 

so as to close the exhaust valves earlier, it will 
cause a higher compression, but would result in later 
opening of the valves ; therefore, what is gained in 
compression by closing the valves earlier, is partly 
lost by late opening on the other side of the piston; 
besides, it robs the engine of power and economy. 
Right here we begin to appreciate engines that are 
equipped with two eccentrics; however, with the 
single eccentric, some means must be provided to 
obtain sufficient cushion to bring the piston and the 
reciprocating parts to a state of rest at the end of the 
stroke. This can be accomplished by raising the 
boiler pressure providing the boiler will permit, 
which will cause an earlier cut-off and a lower ter- 
minal pressure, as well as an increase of economy. 
If the boiler will not permit, the eccentric should be 
advanced so as to admit live steam into the cylinder 
just before the piston completes the stroke, which 
assists the compressed exhaust steam in forming 
cushion. This is shown when the admission line on 
the diagrams lean slightly outward, but pains must be 
taken in doing this work, so as not to admit steam 
too early and cause a counter motion on the piston. 
Fig. 19 also has twenty pounds compression. To 
determine the cushion on the head end, the partial 
vacuum on the other side of the piston at the instant 
it comes to a stand still must be added. This is meas- 
ured on the crank end diagram, at a point as shown 
by the dotted line, which is ten pounds, there being 
ten more pounds atmospheric pressure on the head 
end, to which is added twenty pounds compressed 
exhaust steam, giving thirty pounds cushion, or three 



44 



Practical Application of the Indicator. 



times as much cushion as Fig. 18 ; yet, the exhaust 
valve closed at the same point. When this is carried 
to extreme, it has the same effect as a too early ad- 
mission and will cause the engine to pound. 

The cushion of the crank end is determined in like 





-Scale of Spring 40. 

manner, by adding the partial vacuum of the head 
end to the compression of the crank end. The loop 
in the diagrams is caused by a too light load and the 
expansion curve falls below the atmospheric line, 
showing a loss of economy, as it takes that much 



Practical Application of the Indicator. 



45 



more steam on the admission side of the piston to 
overcome it, as it forms a counter motion on the pis- 
ton, and were it not for the motion of the fly wheel, 
the engine would stop. This can be remedied by low- 
ering the boiler pressure until a suitable release pres- 
sure is obtained. When the back pressure is enough 
greater than the partial vacuum formed in the cylin- 
der near the end of the stroke as represented by the 




Fig. 20— Scale of Spring 40. 

loop in the diagrams ; the exhaust valves will raise 
from their seats which causes a rattling sound, the 
same as is heard before the engine stops after steam 
is shut off. 

Fig. 20 represents the area of trie cushion as shown 
by the dotted portions and can be accurately deter- 
mined with a planimeter ; but unless the diagrams 
are both taken on the same card the latter end of the 
expansion curve of the other diagram must be trans- 
fered from the point where it should cross the com- 



46 Practical Application of the Indicator. 

parison curve of this diagram. This can be done ac- 
curately by making a pinhole at each end of the at- 
mospheric line of each diagram ; then place the dia- 
gram to be transferred on a piece of glass and the 
other directly above it so that the pinholes match 
and when viewed from a strong light the pencil mark 
of the diagram underneath can be plainly seen and in 
this manner can be conveniently transfered. 

Supposing that the same steam pressure be ad- 
mitted into the cylinder of an engine during the entire 
stroke when it would do a certain amount of work 
while at one-half stroke with the same pressure it 
would do one-half the work and so on. So it is with 
the cushion as it depends as much upon the length of 
the area embraced in the cushion as the height. In 
Fig. 20 the diagram shown at the left representing a 
diagram from a Corliss condensing engine where it 
was necessary to make up the deficiency in cushion 
by admitting live steam into the cylinder before the 
piston had completed the stroke as shown by the ad- 
mission line leaning outward, thus admitting the full 
pressure or 75 pounds cushion which is measured 
from the top of the termination of the release curve 
of the diagram from the other end of the cylinder as 
shown, while the cushion of the non-condensing 
diagram as shown at the right is 29 pounds which 
is formed by compressed exhaust steam. Yet the 
area in the shaded portion of this diagram is greater 
thus showing that this diagram has greater re- 
tarding power to stop the piston while the height 
of the cushion on the other diagram is 46 pounds 
greater. 



Practical Application of the Indicator. 47 

To admit the full pressure before the piston has 
completed the stroke so as to make up the deficiency 
in cushion when it becomes necessary, is regarded as 
an objectional feature by some engineers, but it will 
be seen from the above illustration that it is practical 
to make up the deficiency in cushion with live steam 
when the cushion from the exhaust steam is insuf- 
ficient. But as I have before stated, pains must be 
taken not to admit the pressure too early and cause 
a counter motion on the piston. 

In setting the valves on Corliss engines without the 
indicator, the question as to whether or not to lap the 
exhaust valves, has been frequently discussed the world 
over, but like all other types of engines, it depends 
upon too many conditions to lay down a definite rule ; 
however, it depends principally upon the speed of the 
engine ; weight of the piston and the reciprocating 
parts ; pressure in the cylinder at the time the ex- 
haust valves closed, pressure on the expanding side of 
the piston at the time the piston comes to a stand 
still ; temperature of the cylinder walls ; the amount 
of clearance, and with small amount of clearance ; 
high temperature of cylinder walls ; low pressure on 
the expanding side of the piston, when it comes to a 
stand still, and high back pressure in the cylinder at 
the time the exhaust valves closed, all of which will 
cause higher cushion and a closing of the exhaust 
valves at the same point. 

When setting valves without the indicator, it is 
well to examine into these conditions, but at best, it 
is merely supposition and guess work. 



48 



Practical Application of the I?idicator. 



DIAGRAMS FROM CORLISS CONDENSING ENGINE. 

Fig. 21 shows the general features of well formed 
indicator diagrams from a Corliss condensing engine. 
The object of attaching a condenser to an engine is 
to obtain greater economy, but it will show economy 




Fig. 21— Scale of Spring 40. 



only when conditions are favorable. To credit the 
condenser as the gain in efficiency equal to the per- 
centage of the total load carried by the condenser is 
a blunder pure and simple and like many of the tests 
that are being made on steam powers, they are worth- 
less and misleading. 



Practical Application of the Indicator. 49 

The real economy of an engine is based on the 
amount of heat expended in furnishing it with steam 
and this bears no fixed relation to the percentage of the 
total load carried by the condenser or the amount of 
feed water consumed. The thermal unit basis takes 
into consideration all the various items, and reduces 
the performance of each engine to a standard that is, 
comparable, in that credit is given for the energy ex- 
pended in doing the work. It is the only true method of 
comparison and is especially worthy of adoption where 
a test is to be made in which the condenser and dif- 
ferent types of engines are to be put into competition. 
The partial vacuum in the cylinder is measured on 
the scale of the spring from the back pressure line to 
the atmospheric line G G, which is ten pounds, while 
the partial vacuum in the condenser is greater, as 
there is a loss of vacuum between the cylinder and 
condenser about the same as there is a loss of pressure 
between the boiler and engine. The exhaust valves 
should open quickly near the end of the stroke so as 
to bring the expanded pressure down where it belongs 
before the piston starts to return, and should remain 
open until it is necessary for it to close to form com- 
pression so as to obtain a vacuum in the cylinder as 
near full stroke as it is possible. The condenser sim- 
ply removes atmospheric pressure on the exhausting 
side of the piston. Thus, if the mean effective vacuum 
is ten pounds the atmospheric pressure on the admis- 
sion side of the piston is ten pounds greater, plus the 
mean effective steam pressure, which, we will suppose, 
is thirty pounds; this gives a total mean effective 
pressure (M.E.P.) of forty pounds. 



50 Practical Application of the Indicator. 

Suppose it be desired to determine the cushion of 
the head end; first locate the lines of perfect vacuum 
on the scale of the spring. Then measure the com- 
pression on the head end diagram from the line of 
perfect vacuum which, in this case, is fifteen pounds 
absolute pressure, and is about as much as can be ex- 
pected unless the clearance be extremely small, from 
the fact that the atmospheric pressure in the cylinder 
was only five pounds at the time the exhaust valve 
closed. Had this pressure been fifteen pounds, or 
three times as great, which it would, at least, have 
been in a non-condensing engine, the compression 
would also have been three times as great, or forty- 
five pounds, and the exhaust valve been closed at the 
same point. This is the reason why engines run noisy 
when condensing, and a readjustment of the valves is 
necessary. The pressure on the other side of the 
piston is measured on the crank end diagram from 
the line of perfect vacuum to a point as shown by the 
dotted line, which is eight pounds, and must be de- 
ducted from the compression of the head end, which 
gives a cushion of seven pounds; not enough for Cor- 
liss engines running at the ordinary speed, and will 
cause them to pound; therefore, some means must be 
provided to make up the deficiency. To accomplish 
this, some engineers have many peculiar wild-cat 
schemes which are oftimes amusing as well as costly. 
However, it may be accomplished by advancing the 
eccentric so as to admit live steam into the cylinder 
just before the piston completes the stroke, and will 
be shown on the diagrams by the admission line lean- 
ing slightly outward. But pains must be taken in 



Practical Application of the Indicator. 51 

doing this work so as not to admit the live steam too 
early and cause a counter-motion on the piston. 

The cushion of the crank end diagram is deter- 
mined in like manner by measuring the compression 
of the crank end diagram, from which deduct the 
pressure on the other side of the piston, at the time 
it comes to a stand still, which is measured on the 
head end diagram at a point as shown by the dotted 
line. 



CHAPTER VI. 

SETTING CORLISS VALVES WITH THE INDICATOR. 

While the Corliss engine, as manufactured by the 
different makers, varies considerably in its details, a 
general understanding of the type as here illustrated 
and described, and the method of adjusting, will ena- 
ble any one to readily adjust the valves in any of the 
different makes of this style of engine. In the man- 
ner of adjusting with the indicator it is necessary that 
certain preliminary adjustments be made; first, that 
the rocker arm A, as shown in Fig. 22, to which the 
eccentric rod B is connected, shall vibrate to equal 
distances each side of a plumb line from its center of 
vibration, when it is a horizontal engine and setting 
level. This may be determined with the engine run- 
ning slow, or by revolving the eccentric on the shaft,, 
and at the extreme positions of the rocker-arm, with 
a tram, make the marks C D usually on a smooth 
board placed near by. Then equally divide the dis- 
tance between C and D as indicated by E represent- 
ing a center-punch mark; next, place the engine so 
that the tram will span the distance between the 
rocker-arm and E, and adjust the length of the eccen- 
tric rod so that the rocker-arm is plumb and at right 
angles to the eccentric rod; after which, hook in the 
hook-rod F, as shown in Fig. 23, and adjust the 
length of hook-rod so that the mark on back hub of 
wrist-plate G coincides with center mark on wrist- 

52 



Practical Application of the Indicator. 



53 



plate stand; when the wrist-plate will be in its cen- 
tral position (if the plumb-bob be submerged in water 
it will more quickly bring it to a state of rest) ; then, 




Fig. 22. 



with steam valves hooked in, take off back bonnets 
of steam valves at the side of cylinder opposite the 
wrist-plate and pull valves out flush with the end of 
chambers and adjust the length of steam valve rods 



54 



Practical Application of the Indicator, 



by means of the right and left thread at their opposite 
ends so that the steam valves will have lap according 
to the table, and the dividers will span the distance 
between the marks H and I, H representing the work- 
ing edge of the port, and I the working edge of the 
valve. Lengthen the rods for greater lap and shorten 
for less. On engines with valves opening in the op- 



d: 



' -I— V 




\ v 



/ / 










Fig. 23. 



posite direction the difference in adjustment is to set 
the lap on the other side of the port. Any prelimi- 
nary adjustment of the exhaust valves is unneces- 
sary, because their proper positions are determined 
by use of the indicator, and this bears no fixed 
relation as to whether they are lapped, edge to 
edge, or open. 



Practical Application of the Indicator. 55 

TABLE FOR SETTING LAP OF STEAM VALVES. 



Diameter 


Lap 


Diameter 


Lap 


of 


of Steam 


Of 


of Steam 


Cylinder. 


Valves. 


Cylinder. 


Valves. 


IO 


% 


24 


H 


12 


% 


26 


Vs 


14 


5-i6 


28 


y 


16 


5-16 


30 


H 


18 


5-16 


32 


7-16 


20 


5-i6 


34 


7-16 


22 


h. 


36 


7-16 



The amount of lap on steam valves with wrist 
plate on center varies among the different builders 
about 1-16", more or less, from that given in the 
table; some giving about 1-16" more, others about 
1 -16" less. With less lap when the valves are at a 
point of opening, the eccentric is in a position to 
give the valves a more rapid opening, thus realizing a 
higher pressure in the cylinder; but the position of 
the eccentric must also be correspondingly later in 
order to have the same amount of lead, and this 
brings about a later action of the exhaust valves. 
With high terminal pressure, the exhaust valves in 
some of the engines, when equipped with a single 
eccentric, are not sufficiently rapid in their action 
to give a proper release and compression, and this 
loss of time more than balances what is gained in 
'realizing a higher pressure in the cylinder from the 
small amount of lap. When it is found necessary 
to give more lap on steam valves than that given 
in the table in order to give proper action to the 
exhaust valves, the motion is not of a modern 
character. 



56 



Practical Application of the Indicator. 



With nearly all engines of present construction 
the amount of lap, as given in the table, will answer 




Fig. 24. 



the requirements of the different conditions in a most 
satisfactory manner, while a slight variation of more 



Practical Application of the Indicator, 



57 



or less lap may better suit the requirements in a 
few foreign conditions. 

To adjust the length of the dash pot rod J, as 




Fig. 25. 



shown in Fig. 24, place the wrist-plate so that the 
right-hand mark on wrist-plate stand coincides with 
mark on the back hub of wrist-plate, and with the 



58 Practical Application of the Indicator. 

dash pot piston properly seated, adjust the length of 
the dash pot rod so that the block K will clear the 
hook L an equal distance on top and bottom; then 
place the wrist plate in the other extreme position 
and adjust the other rod in like manner. The collar 
M, as shown in Fig. 25, should be fastened at a 
height to allow the governor to raise enough so as to 
affect a sufficiently early cut-off, which will not ma- 
terially increase the speed of the engine with only its 
friction load and highest pressure. With the gov- 
ernor resting on the projection of the collar N, raise 
the governor until the sleeve O is at a point one-half 
the distance toward the collar M, block it and adjust 
the side rod P until the double bell crank Q is per- 
pendicular, when the governor will be the most sen- 
sitive; then lower the governor so that it again rests 
on the projection, and with the wrist-plate in the posi- 
tion as shown in Fig. 26, so that the left hand mark on 
the wrist-plate stand coincides with the mark on the 
back hub of wrist-plate, adjust the governor rod R so 
that the tripping cam S just touches the tail of the 
hook, and adjust the other rod in like manner. 

The automatic safety stop consists of the collar 
N, about the vertical governor shaft, having on one 
side a projection through which is a pin to receive 
the groove underneath the side rod collar T. This 
collar is stationary on the side rod P, and rests on 
the projection of the collar N, when the governor 
is in its lowest working range; as soon as the gov- 
ernor raises a spring in connection with the collar N, 
swings the projection away from the path of the side 
collar T, and should the governor belt break the side 



Practical Application of the Indicator. 



59 



collar T will clear the projection of the collar N and 
drop to its lowest extremity, when the safety cams 




Fig. 2 



U will prevent the hooks from engaging. The steam 
valves will then remain closed and the engine Will 



60 Practical Application of the Indicator. 

stop. When it is desired to stop the engine the 
collar N may be swung in place to receive the gov- 
ernor just before the engine stops; thus preventing 
the governor from dropping to its lowest extremity, 
and it will be necessary to raise it again before the 
engine can be started. No Corliss engine should be 
without an automatic safety stop, and the absence of 
one, no doubt, is the cause of many of the disastrous 
bursting of fly-wheels, causing loss of life and de- 
struction of property. Such a device does not depend 
upon the memory of the engineer to pull a pin, or 
make some adjustment by hand, after the engine is 
up to speed, as is the case with many devices in 
order to make them effectual, To adjust the safety 
cams, place the wrist-plate in the position as shown 
in Fig. 24, and adjust the cams so that it just touches 
the tail of the hook, when the governor is resting on 
the collar N, and adjust the other cam in like manner. 
To test the adjustment, lower the governor to its low- 
est extremity and vibrate the Wrist-plate in both ex- 
treme positions. Should the hooks engage, move 
these cams upward until the hooks disengage. 

The plunger rod V of the oil pot W should be 
adjusted so the plunger will clear on top and bot- 
tom when the governor is in its highest and lowest 
positions. The substance used in the pot is usually 
engine oil diluted with kerosene, so as to permit the 
governor to more quickly respond to the variations of 
load. With most of the pots now in use the kero- 
sene alone has not sufficient body to steady the gov- 
ernor, thus causing it to fluctuate, which make varia- 
tions in the cut-off when there are no changes in load. 



Practical Applicatio?i of the Indicator. 



61 



To reverse the engine only requires to set the 
eccentric so that it has the same degrees of advance- 
ment on the other side of the crank and not a half 
turn on the shaft, unless its previous position was 90 
deg. in advance of the crank. 

To increase the speed of the engine the. gover- 




Fig. 27— Scale of Spring 40. 



nor pulley must be larger, and to decrease, smaller. 

The remaining adjustment of the valves are made, 
by use of the indicator. 

Should the results be a pair of diagrams similar to 
those represented in Fig. 27, H representing the head 
end, and C the crank end, the admission lines lean 



'62 Practical Application of the Indicator. 

inward, which indicate insufficient lead, causing loss 
of power and economy. The distance along the 
dotted lines from the completion of the admission 
lines to the lines A, which is located by a right angle 
perpendicular to the atmospheric lines, is \" . The 
length of the diagrams is 3J", and the length of the 
stroke of the engine is 42". 

Now, as 3=. 25, and 3^ = 3.5: 

Thus .25X42 



3-5 
which is the distance the piston moved before the full 
pressure was admitted. The exhaust valves are cor- 
respondingly late, both in opening and closing, be- 
cause the expanded pressure is not fully released until 
the piston has traveled on its return stroke the 
distance equivalent to the length of the dotted line 
along the end of the diagrams. The compression is 
only seven pounds, and the pressure on the other side 
of the piston at the end of the stroke is ten pounds. 
This is three pounds more pressure per square inch on 
the opposite side of the piston than the compression, 
and instead of having cushion, the tendency would be 
to send the piston still further, were it possible to do so. 
Many engines are being run under just such abus- 
ing conditions, and ofttimes worse, and it is not to be 
wondered at that it requires liberal use of lubrication, 
frequently hot crank pin, etc. , as well as a noisy en- 
gine. If engineers would make frequent use of the 
indicator the engine would require less attention, and 
looking at it from a commercial standpoint, at the 
rate of dollars and cents, for those who must pay for 



Practical Application of the Indicator. 63 

the fuel and repair bills, the indicator is an indis- 
pensable adjunct to every engine. The economical 
running of the engine and the practical application of 
the indicator should be thoroughly understood by 
every man who aspires to the calling of an engineer. 
It is plain to be seen that the engine is late all around, 
but before advancing the eccentric, attention should 
be given to the exhaust valves, that they are suffi- 
ciently closed before the steam valves open, so that 
the entering steam does not pass into the exhaust, in 
which case the admission would appear too late, if it 
really were early enough. This is indicated by ab- 
sence of compression. The compression shown in 
these diagrams is sufficient to accomplish this result. 
Therefore, the first adjustment to be made is to ad- 
vance the eccentric until the admission lines are per- 
pendicular. The exhaust valves will open earlier, 
causing a more perfect release and an earlier closing, 
causing a higher compression. Should the compres- 
sion be too high, and the release still a trifle late, 
shorten the exhaust valve rods, which will result in 
an earlier opening and a later closing; and should the 
release be too early and compression too low, lengthen 
the rods accordingly. Again, supposing the results 
should be a pair of diagrams similar to those repre- 
sented in Fig. 28. The admission lines lean outward, 
which indicate too early lead, because steam was 
admitted into cylinder before the piston had com- 
pleted the stroke at an equivalent distance to that 
represented by the dotted lines. That the admission 
is too early is plain to be seen, because the upper line 
indicates the piston going ahead and the lower line 



64 



Practical Application of the Indicator. 



coming back, and if steam was not admitted into the 
cylinder until the piston had completed the stroke, as 
it should, neither would the admission line start to 
erect until at the end of the diagram. The com- 
pression is high, and an additional amount of live 




Fig. 28— Scale of Spring 40. 

steam will more than stop the piston at the end of the- 
stroke, thereby forming a counter-motion, and re- 
quires an additional amount of steam, which is a loss 
of power and economy. Should the exhaust valves 
close so early that the compression equals the highest 
admission pressure there would be no admission lines 
and the exhaust valve rods should be shortened so as 



Practical Application of the Indicator. 



65 



to lower the compression about equal to that of Fig. 
28, then the eccentric should be set back until the 
admission lines be perpendicular, which at the same 
time will lower the compression. Should the com- 
pression be too low after the eccentric has been set 
back so that the admission lines are perpendicular^ 




Fig. 29— Scale of Spring 40. 

the exhaust valve rods should be lengthened until a 
higher compression be obtained. 

Obtaining the same form of admission lines from 
both ends of the cylinder cannot always be accom- 
plished with the eccentric. Frequently the admission 
lines obtained will be similar to those represented in 
Fig. 29. The head end admission line leaning as 
5 



66 Practical Application of the Indicator. 

much outward as the crank end one leans inward — 
principally due to the angularity of the eccentric rod. 
Should the exhaust opening and closing be late, the 
eccentric should be advanced until the admission line 
of the crank end is perfect. This will usually bring 
the exhaust valves around so they will perform their 
proper duties. But the admission of the head end 
will be still earlier, which can be remedied by length- 
ening the head end steam valve rod, thereby increas- 
ing the lap until the admission at this end also is 
perfect. This necessitates a readjustment of the 
governor rod and dash pot rod on the head end. 
Should the opening and closing of the exhaust valves 
be too early, the eccentric should be set back until 
the admission line of the head end is perfect, when 
the exhaust valves will be sufficiently later, but the 
admission of the crank end will be still later. This 
can be remedied by shortening the crank end steam 
valve rod which decreases the lap until the admission 
of this end also is perfect, and a readjustment of the 
governor rod and dash pot rod on the crank end 
must be made. The indication of the opening and 
closing of the exhaust valves from the diagrams, 
as shown in Fig. 29, are perfect, therefore the ec- 
centric should remain in this position, and the steam 
valve rods on both ends of the cylinder should be 
altered, lengthening the head end and shortening 
the crank end. 

To equalize the cut-off is the last adjustment to 
be made. This can be determined on the steam lines 
by the distance from the commencement of the dia- 
grams to the points of cut-off. Should the cut-off on 



Practical Application of the Indicator. 



67 



the crank end be the earlier as shown in Fig. 30, it is 
only necessary to shorten the crank end governor rod, 
which will set this tripping cam further away until 
the cut-off is equal. Where the load is constantly 
changing and when only one indicator is used, it is 
frequently connected with side pipes in a three-way 




Fig. 30— Scale of Spring 40. 



cock or T with an angle valve at each end and a dia- 
gram is taken from each end of the cylinder on the 
same card as shown in Fig. 31, and the pencil should 
be applied about four revolutions and about three 
different times each side of the piston. 

In this manner the average points of cut-off are 
more closely determined than if all the revolutions 



68 Practical Application of the Indicator. 

were taken at one time on each side of the piston. 
Should the head end be the earlier, lengthen the head 
end governor rod which will have the same effect on 
this end. With valves opening in the opposite direc- 
tion the governor rod of the head end must be short- 
ened to effect a later cut-off and the crank end 




Fig. 31— Scale of Spring 40. 



lengthened. While this may be quickly equalized by 
partly closing the throttle valve until the valves trip 
only a part of the time and it can readily be de- 
tected if they trip and pick up equally. This will 
disturb the adjustment of the safety cams of the 
automatic safety stop and a readjustment becomes 
necessary. 



CHAPTER VII. 

DIAGRAM FROM STEAM PIPE. 

Fig. 32 shows a cylinder and steam pipe diagram 
with boiler pressure line added. A A is the boiler 
pressure line which is located by measurement on the 
scale of the spring at such a distance above the at- 
mospheric line as to represent the boiler pressure by 
gauge at the time the cylinder diagrams were taken 




Fig. 32— Scale of SrmNG 40. 

The diagram between the boiler pressure line and the 
cylinder diagram is that portion of the steam pipe 
diagram belonging to that end of the cylinder and if 
taken separately, must be located by measurement at 
such a distance above the atmospheric line on the 
cylinder diagram as its distance is above the atmos- 
pheric line of the steam pipe diagram. B is taken 

69 



70 Practical Application of the Indicator. 

when no steam 'is admitted into the cylinder and rep- 
resents the highest pressure realized at the point the 
steam pipe diagrams were taken. The distance be- 
tween B and the boiler pressure line represents the 
loss of pressure by radiation between this point and 
the boiler. C is taken during the time that steam is 
admitted into the cylinder and represents by its dis- 
tance between it and B, the loss of pressure at that 
point during admission. If the indicator is attached 
above the throttle valve the distance between C and 
the boiler pressure line, represents the loss of pressure 
between the boiler and the point above the throttle 
valve during admission. If the indicator be attached 
below the throttle it represents the loss of pressure 
between the boiler and that point, and so on. The 
distance between C and the steam line of the cylinder 
diagram represents the loss of pressure between the 
cylinder and the point above the throttle or any other 
point of attachment. When steam is cut off the pres- 
sure in the pipe is restored and C rises correspond- 
ingly, and should merge into the line B, but it 
generally causes the pressure at this point to fluctuate 
above B and frequently a trifle above the boiler pres- 
sure line as shown. With long steam pipes and ex- 
cessive loss of pressure between the boiler and engine 
the fluctuation is constantly taking place and is shown 
by a rising and falling of pressure at other points of the 
diagram about the same as when two or more engines 
are being supplied from the same main. For con- 
venience the steam pipe and cylinder diagram should 
be of equal length, otherwise, it requires considerable 
figuring to learn their proportions. 



Practical Application of the Indicator. 



71 



ECCENTRIC TOO LATE. 

Fig. 33 shows a pair of diagrams taken from a 
14" X 36" Corliss engine, where the superintendent 
had never run an engine and knew practically nothing 
concerning it, but thought himself more proficient in 
the science of adjusting valves than his engineer, and 
he proceeded to adjust the valves on his engine by 
the rule of the thumb. The results are not surprising 
as the man attempted to do something without know- 




Fig. 33— So-ale of Spring 60. 



ing how to do it. After the engine had run a few 
months he desired to have a pair of indicator diagrams 
taken from -it by an expert only as a matter of interest 
because any readjustment of the valves he knew was 
unnecessary. After the valves were properly adjusted 
with the indicator, the fuel bill was nearly cut in two, 
and the superintendent was forced to acknowledge 
that the thumb rule for setting engine valves was 
neither practical nor profitable. 



72 Practical Application of the Indicator. 

The admission is late and the exhaust valves are 
still open after the piston has started on its return 
stroke causing the entering steam to pass into the ex- 
haust and the admission lines follow the back pressure 
line a short distance. When the exhaust valves close, 
thus preventing the entering steam from passing into 
the exhaust, the admission lines rise, but owing to the 
fact that piston has already moved a considerable dis- 
tance the highest pressure is not realized on the 
crank end until at the point of cut-off. The ex- 
haust valves are late in opening and the pressure 
near the termination of the expansion curve of the 
crank end is six pounds, which on account of hav- 
ing no compression, would tend to send the piston 
still further at the head end were it possible to do so. 

The pressure near the termination of the expan- 
sion curve of the head end is four pounds, which 
would tend to send the piston still further at the 
crank end. The engine sounded like the drop of a 
pile driver at each end of the stroke. The connec- 
tions were frequently hot and most of the engineer's 
time was occupied in oiling and keying up. 

The cut-off is unequal and the automatic safety 
stop was ineffectual and the whole job needs no 
further description. The vibration of the rocker arm 
was first adjusted; then lap of the steam valves was 
set and other necessary adjustments made, such as 
the governor, dash pot rods, etc., after which the 
eccentric was advanced about one inch on the shaft, 
which brought a perfect admission and release, and 
the compression still being insufficient the exhaust 
valve rods were lengthened. 



Practical Application of the Indicator. 



73 



DIAGRAMS FROM THE SAME ENGINE, BEFORE AND AFTER 
ADJUSTING WITH THE INDICATOR. 





Fig. 34— Scale of Spring 40. 



Fig. 34 is taken from a 20" x4 2 " Corliss engine; 
revolutions, 60; boiler pressure, 85. This engine 
had been in use many years and the diagrams in 



74 Practical Application of the Indicator. 

question were the first ones taken from it, and their 
features show almost everything but economy. The 
release pressure is too high and a vast volume of 
steam at high pressure which could yet do useful 
work is exhausted into the atmosphere. The exhaust 
valves are late in opening and the minimum back 
pressure of the crank end is 3J pounds. The crank 
end exhaust valve closes too early and forms 54J 
pounds compression, as shown at A. When the 
piston begins its return stroke the steam valve re- 
mains closed and the pressure falls to B, the valve 
then opens, but the highest pressure is not realized 
until the piston has traveled about nine inches, 
causing a loss of 27 pounds pressure between this 
end of the cylinder and the boiler. 

The admission on the head is also late, which is 
caused either by open exhaust valve (because there 
is no compression) or by absence of lead, and the 
loss of pressure between this end and the boiler is 
16 pounds. The points of cut-off are poorly de- 
fined, caused by the steam valves being slow in their 
action while closing. The release pressure of the 
head end is 16 J- pounds and the minimum back 
pressure is not obtained until the end of the stroke. 

After the valves were properly adjusted other 
conditions were examined and also found to be any- 
thing but economic, as the loss of pressure between 
boilers and engine was 14 pounds, yet the distance 
was short. Steam pipe diagrams were taken and 
the loss of pressure through the throttle valve, steam 
chest and ports was found to be slight. The exces- 
sive loss being in the steam pipe, which was imper- 



Practical Application of the Indicator. 75 

feet in every detail; no provisions having been made 
for unequal expansion or contraction, and its small 
size and unnecessary bends were responsible for the 
loss of power and economy. This great difference of 
pressure tends to bring water from the boilers, and 
there being no separator in the steam pipe conse- 
quently the condensation and water entrained in the 
steam passed into the cylinder, thus affecting its effi- 
ciency as well as the lubrication. Kerosene was 
also used in the boilers in great quantities as a scale 
preventative, and the kerosene must pass through 
the engine cylinder, which also destroys a perfect 
lubrication, and it is no wonder the valves and 
piston were in a very leaky condition. These were 
put in order and the steam pipe replaced with one 
of ample size and proper construction, being pro- 
vided with a separator which returned the water 
automatically to the boilers by means of a steam 
loop, which is the best cf the many devices known. 
Some steam users consider that if the engines and 
boilers are of modern type the rest of the plant is 
good enough and can take care of itself. The im- 
portance of having a properly piped steam plant has 
been too long neglected, and I feel safe in stating 
that a very large percentage of the steam plants in 
use to-day are in such a defective condition as to 
render them both costly and dangerous, and it is 
to be hoped that at no distant date steps will be 
taken toward bringing this important factor of the 
steam plant to a degree of perfection. 

The excessive back pressure was not caused 
through any fault of the exhaust pipe, but was due 



76 



Practical Application of the Indicator. 



to insufficient area of the exhaust ports, and this 
defect was also remedied. After the alterations were 
made, over which I had personal supervision, and 




Fig. 35— Scale of Spking 40. 



the valves properly adjusted, all the machines of the 
factory were put to work at full capacity for the 
purpose of determining the capacity of the engine. 
While before it had been too small, it was now more 



Practical Application of the Indicator. 



77 



than ample, and Fig. 35 was obtained. The loss of 
pressure between the boilers and engine is only 2 
pounds and a fraction; the back pressure line merges 
into the atmospheric line and the working of the 
entire valve gear produced a pair of indicator dia- 
grams that it is hard to believe come from the same 
engine. There are many men traveling around the 
country who style themselves indicator experts, and 
profess to make complete and accurate tests of 
steam plants. I have noted several instances where 




Fig. 36— Scale of Spring 40. 

these so-called experts have made what they con- 
sidered a complete test, and invariably found it to 
be the case that they had simply adjusted the valves 
of the engine so as to secure a diagram that would 
pass inspection, and had not taken into considera- 
tion any of the other important factors. Such tests 
are expensive as well as incomplete. 

GOOD ADJUSTMENTS BY A NOVICE WITH THE INDICATOR. 

Fig. 36 shows a pair of diagrams from a i6"x4 2 " 
Corliss engine. Diameter of piston rod, 2 15-16"; 



78 Practical Application of the Indicator. 

lap on sceam valves, 5-16"; revolutions, 48; boiler 
pressure, 80. The valves of this engine were ad- 
justed and the diagrams taken by a young man who 
had only a very limited experience with the indicator, 
but he rapidly perfected himself in its use by receiv- 
ing personal instructions as to its practical appli- 
cation and the study of practical works on the 
subject. In the present epoch of improvement and 
advancement, length of service is not now such an 
important factor as capability. The indicator may at 
first seem a broad scope to the beginner, which is true, 
from the fact that it embraces the most valuable, im- 
portant and scientific factors in the science of steam 
engineering. If the author presents the instruction 
to the student in a comprehensive, reliable and at- 
tractive manner, what to do and how to do it and 
why it should be done, any intelligent engineer or 
practitioner having a reasonable mechanical knowl- 
edge can, in a short time, perfect himself so as to be 
thoroughly capable of correctly applying the indicator 
and skillfully make all the adjustments upon the en- 
gine so as to obtain an economical departure in the 
working of steam, and secure a smooth running en- 
gine, as well as to make the necessary calculations 
from the diagrams in a scientific and systematic man- 
ner. The indicator unfolds a picture of the perform- 
ance that takes place inside of the steam engine 
cylinder which would otherwise be enveloped in mys- 
tery, and guides the engineer accurately in setting the 
valves of all the different styles of engines by a 
method that is easily and readily comprehended by 
any intelligent engineer, and there is no other device 



Practical Application of the Indicator. 79 

that so thoroughly teaches and qualifies an engineer 
as a first-class indicator. The degree of perfection 
which this young man has attained in the handling of 
the steam and exhaust valves only proves what I have 
before stated, that any man with ordinary intelligence 
can, with the indicator, soon learn to keep his engine 
in the most economical working condition. The 
steam is admitted and released at the right time; the 
compression is moderate and the cut-off is practically 
equal; the steam lines falls slightly as the piston ap- 
proaches the point of cut-off, and is no fault of any 
of the adjustments made upon the engine, but is due 
to insufficient area in the steam passages. The loss of 
pressure will be the greatest at a point in the cylinder 
when the crank is at right angles to the connecting 
rod, at which time the movement of the piston is the 
fastest. The small waves at the commencement of 
the expansion curve are caused by fluctuations of the 
pressure in the cylinder, due to the rapid falling of 
pressure as compared with the distance the piston 
moves away. If steam be cut off at one-fourth 
stroke (clearance neglected) the piston must move 
only from one-fourth stroke to one-half stroke when 
the volume is doubled, while from one-half stroke it 
must move to the end of the stroke, or double the 
distance, before the volume is again doubled from 
what it was at one-half stroke. The most rapid 
change of volume is, therefore, immediately after the 
earliest point of cut-off, when the piston moves the 
shortest distance to change the volume. The sudden 
change of pressure causes the pressure to fluctuate, 
and generally follows with oscillations of the indica- 



80 Practical Application of the Indicator 

tor piston and forms a wavy expansion curve at this 
point. On high-speed engines, where the piston is 
moving rapidly away, the wavy expansion curve may 
continue to the end of the stroke. The fluctuation 
of pressure in the cylinder immediately after the point 
of cut-off, also is due to condensation, because the 
temperature of the steam at this pressure exceeds the 
temperature of the cylinder. When the steam has 
expanded so that its temperature does not exceed the 
temperature of the cylinder, the fluctuations from 
this cause have practically ceased. When the waves 
are symmetrically rounded, as they will be when taken 
with a sensitive instrument, they do not destroy the 
truth of the diagram. 

DIAGRAMS SHOWING DIFFERENT EFFECTS IN CUSHION 
WITH AND WITHOUT THE CONDENSER. 

Fig. 37 shows a pair of diagrams from a i6"x36" 
Corliss non-condensing engine. Revolutions, 80. 
Fig. 38 is taken from the same engine, with condenser 
attached, and without readjusting the valves. The 
difficulty in this case was, as stated by the operator, 
that, when running non-condensing the engine run 
practically noiseless, but when the condenser was at- 
tached the engine pounded badly, for which they were 
unable to account and could not remedy. Frequently 
inquiries are being made as to why engines run noisy 
while condensing, and how it may be remedied. But 
few condensing engines at the present time are run- 
ning smooth and with proper action of the exhaust 
valves, for the reason that this subject has not been 
thoroughly understood. Referring to Fig. 37, the 



Practical Application of the Indicator. 



SI 



cushion on both ends is 23 pounds, and in this case, 
when both diagrams are taken on one card, instead 
of measuring the compression and deducting the 




pressure above the atmosphere, or adding the vacuum 
below on the other side of the piston at the instant 
it comes to a standstill, it is only necessary to meas- 



82 



Practical Application of the Indicator. 



ure from the top of the termination of the expansion 
curve to the point intersecting the admission lines, 
as shown by the length of the dotted lines. 




The absolute back pressure is I 5 pounds, and the 
compression is 45 pounds. When the condenser is 
attached, as shown in Fig. 38, having 10 pounds 



Practical Application of the Indicator. 83 

vacuum, or a remainder of five ppunds atmospheric 
back pressure, or one-third as great as when non- 
condensing. The compression can only be one-third 
of 45, which is 15 pounds, and in this case the ter- 
minal pressure on the opposite side of the piston is 
1 5 pounds, therefore the pressure is equal on both 
sides of the piston, and there is no cushion. This is 
the reason that engines run noisy when condensing, 
and a readjustment of the valves is necessary. The 
necessary cushion can be obtained by advancing the 
eccentric until the pounding has ceased, thus admit- 
ting live steam into the cylinder a trifle before the 
piston has completed each stroke, and the admission 
lines will lean outward. This will also cause the ex- 
haust valves to open earlier, and should they then 
close too early and choke off the condenser the ex- 
haust valve rods should be shortened, which will cause 
an earlier opening. If this does not give proper action 
to the exhaust valves, and unless they have the max- 
imum amount of lap, we would suggest an increase of 
the lap, and advance the eccentric accordingly, thus 
giving a still earlier action of the exhaust valves. 

DIAGRAMS FROM OVERLOADED CORLISS CONDENSING 
ENGINES. 

Fig. 39 shows a diagram from a 2o"x42 ff Corliss 
condensing engine. Revolutions, 70. The manipu- 
lation of the indicator in this case only proves that 
unless it is properly made use of, and its reading cor- 
rectly interpreted, and the conclusions based upon 
the diagrams are judiciously made, the indica- 
tor is of no .more value to the engineer than a pair 



84 Practical Application of the Indicator. 

of spectacles are to a blind man. The imperfect 
action of the exhaust valve practically robs the con- 
denser of any value it may have. In order that the 
earliest release might be obtained from any adjust- 
ment made on the exhaust valve rod the compression 
has been lowered to such an extent that the exhaust 
valve is only sufficiently closed at the end of the 
stroke so as to prevent the entering steam from pass- 
ing into the exhaust and the piston has moved a 
considerable distance before the condenser has 




Fig. 39— Scale cf Spring 40. 



succeeded in lowering the back pressure equal to the 
atmospheric, and a reasonable amount of vacuum is 
not obtained until the piston has reached about one- 
half stroke. The release pressure on the diagram 
from the other end of the cylinder was considerably 
greater than the compression, but a part of the de- 
ficiency in cushion is obtained from the entering steam 
which is admitted into the cylinder a trifle before the 
piston has completed the stroke, as shown by the ad- 
mission line leaning slightly outward. Whether the 
steam valves have as much lap as is possible without 



Practical Application of the Indicator. 85 

wire drawing the entering steam to an extent that will 
more than balance that gained by an earlier action of 
the exhaust valves, is a matter of doubt, and should 
this be the case, it proves that the motion is not of a 
modern character. It is true that the majority of en- 
gine builders are not as close readers of the indicator 
as they are generally supposed to be, and this is the 
reason that many of our modern engines are deficient 
in construction rather than principle. Every concern 
that pretends to manufacture an engine proves its 
experiments and substantiates its claims by the aid of 
the indicator, and unless the operator is proficient in 
its use it must necessarily follow that the engine is as 
incorrect as the conclusions based upon the diagram. 
This diagram shows that the engine is overloaded, 
and unless the steam valves have as much lap as is pos- 
sible the lap should be increased, which would neces- 
sitate an advance of the eccentric accordingly, and 
this would bring about an earlier action of the exhaust 
valves so as to give the condenser proper action 
throughout the stroke, and relieve the load carried by 
the steam, which would bring about a more suitable 
release pressure and a gain in economy. 

Fig. 40 shows a pair of diagrams from an 18" 
X42" Corliss condensing engine. Revolutions 60. 
The admission lines on the diagrams lean slightly in- 
ward and indicates a trifle late admission, thus show- 
ing that the eccentric should be advanced a trifle, 
providing the steam valves had the proper amount of 
lap and that the exhaust valves performed their 
proper duties. But the exhaust valves are late as 
they do not commence to open until at the end of the 



86 



Practical Application of the Indicator. 



stroke, and the terminal pressure at the head end is 7 
pounds greater than the compression of the crank 




end, which would tend to send the piston still further 
were it possible to do so. Also on the right hand end 



Practical Application of the Indicator. 87 

of the diagrams the terminal pressure is 5 pounds 
greater, and since the piston speed in feet per minute 
is 420, the revolutions 60, and without any cushion 
the engine cannot help but pound. And this late 
opening of the exhaust valves chokes off the condenser 
at the commencement of its stroke, so that the con- 
denser does not get the proper action until nearly 
one-half stroke. 

The load is too heavy for such a pressure as the 
point of cut-off should take place at a point in the 
stroke so as to bring the expansion curve below the 
atmospheric line near the end of the stroke. 

The steam lines are fairly well maintained which 
indicate an ample area in the steam passages, and a 
rapid opening of the steam valves which is evidently 
accomplished by having small amount of lap on the 
steam valves, in which case the eccentric has less an- 
gular advance in order to obtain the same amount of 
lead, and consequently gives a more rapid opening of 
the steam valves. But this gain cannot balance the 
efficiency, of which the condenser is robbed, therefore 
the lap on the steam valves should be increased which 
would necessitate advancing the eccentric, thus giving 
a more rapid action of the exhaust valves. But, how- 
ever, with such a high terminal pressure the necessary 
cushion cannot be properly obtained, from the fact it 
would choke off the condenser too early at this end of 
the stroke, therefore, since the engine is overloaded, 
and after giving the proper amount of steam lap the 
eccentric should be advanced sufficiently to make up 
the deficiency in cushion by admitting live steam into 
the cylinder before the piston completes the stroke, 
when the admission lines will lean slightly outward. 



■83 Practical Application of the Indicator. 

Fig. 41 shows a diagram from a 14/X42" steam 
jacketed Corliss pumping engine. Revolutions 24. 
The admission line leans inward ? which indicates a 
late admission, and the piston moved a short distance 
before the full pressure was admitted. The steam 
line is maintained in a straight line with the atmos- 
pheric line to the absolute point of cut-off, which, 
however, can be readily obtained in most any Corliss 
engine running at such a slow speed. The point of 




Fig. 41— Scale of Spring 40. 



cut-off is so sharply defined that there is no indication 
of a reduction in the pressure during the time that 
the steam valve is closing, which is also readily ob- 
tained on a slow speed engine that is equipped with 
an independent cut-off. The expansion curve pre- 
sents a beautiful appearance but not knowing the 
percentage of clearance, its truthfulness can not be 
known. However, an approximation of the percent- 
age of clearance not materially differing in the location 
of the clearance line will make but slight variation in 



Practical Application of the Indicator. 89 

the theoretical curve. The exhaust valve does not 
open until at the end of the stroke and a perfect re- 
lease is fully obtained while the engine' is passing its 
center, thus the full amount of vacuum is realized 
before the piston commences its stroke, as shown by 
the perpendicular release line. But the slow speed 
gives ample time for a perfect release. The vacuum 
line is also beautifully maintained and the exhaust 
valve closes at a point in the stroke to give the con- 




Fig. 42— Scale of Spring 40. 



denser proper action. The terminal pressure on the 
diagram from the other end of the cylinder was 4 
pounds greater than the compression of this diagram, 
yet the engine run fairly smooth, from the fact that 
the piston speed in feet per minute is 168, and the 
revolution 24. The engine is overloaded, but had 
the admission line been perfect the diagram would 
have been a subject of beauty. 

Fig. 42 shows a diagram from the head end of the 
cylinder. The admission line leans outward and the 



90 Practical Application of the Indicator. 

full pressure is admitted before the piston comes to a 
standstill, which was found necessary on the head end 
in order to secure smooth running, from the. fact that 
the piston at this end moves faster, the crank end 
having no cushion. As the piston begins its stroke it 
creates a fluctuation in the pressure and forms the 
small hump above the steam line proper. Steam lines 
frequently have many peculiar defects and some of 
them are regarded as a mystery, but are in reality 
simple facts, caused by the disturbance of the pressure 
in the steam passages, and with the Indicator attached 
at these various places, they can be located as pre- 
cisely as on the point of a needle. Frequently steam 
lines have a drop in pressure and again immediately 
rises thus forming a notch, and on a Corliss engine it 
is generally caused by a readjustment of the exhaust 
valves which after a long service have worn only that 
portion of the chamber in which it moves, and as the 
valve passes over the shoulder it gives a sudden leak 
and forms the notch in the steam line. When two 
or more engines are supplied from the same main and 
unless its size is ample, it may cause a wavy steam 
line about the same as caused by a too small steam 
pipe on a single cylinder engine, or an inferior Indi- 
cator may falsify a diagram and cause the engineer a 
great deal of unnecessary labor and thought. 

DIAGRAMS SHOWING LEAKY EXHAUST VALVES. 

Fig. 43 indicates a leak in the exhaust valve, as 
shown by a falling in pressure in the upper portion 
of the compression curve. Had the exhaust chamber 
been free from cuts and wear, it would only have been 



Practical Application of the Indicator. 91 

necessary to replace the valve, but when they are 
both cut the chamber must be re-bored and a valve 
made to fit. The admission line leans inward which 
indicates a too late admission, fiing of indicator 
causing a peak. The sudden drop of pressure in 
the latter portion of the expansion curve is also caused 
from a leak in the exhaust valve, because the lappage 
on the exhaust valve at this point in the stroke is less 
than in the beginning of the expansion curve. The 




Fig. 43— Scale of Spring 40. 

steam valves in this case were practically free from 
leaks, otherwise the leakage of them into the cylinder 
might have balanced the leakage out of the cylinder 
in which case the compression curve would have indi- 
cated no leak. This falling in the compression curve 
may also be caused by leakage in the piston, but if so 
it can generally be detected by a rapid falling of the 
pressure in the expansion curve, immediately after the 
point of cut-off. The only positive method of testing 
the leakage of the valves and the piston is to test 
them without the indicator, from the fact that the 



92 



Practical Application of the Indicator 



leakage into and out of the cylinder may balance each 

other in which case the indicator would indicate no leak. 

Fig. 44 shows a diagram from a 32"x6o" Corliss 




engine. Revolutions, 50. The admission line leans 
slightly outward and indicates a too early admission, 
but still there is a reduction in the initial pressure as 
the highest pressure is not realized until the piston 



Practical Application of the Indicator. 93 

has moved a considerable distance as shown by the 
loss of pressure at the commencement in the stroke 
and was caused from keying up the connections on 
the eccentric rod which disturbed its length and gave 
an unequal vibration to the rocker-arm in which case 
the steam valve on this end of the cylinder was slow 
in its action while opening. The upper portion of the 
compression curve leans outward and indicate a leak 
in the exhaust valve from the fact that the compres- 
sion curve on the diagram from the other end of the 
cylinder was perfectly formed, thus showing that there 
was practically no leak in the piston. Had the com- 
pression curve on the diagram from the other end of 
the cylinder also showed a leakage out of the cylinder 
it would indicate a leak in both exhaust valves, or the 
piston or both. 

A DISTORTED DIAGRAM CAUSED BY IMPERFECT 
REDUCING MOTION. 

Fig. 45 shows a diagram taken from a Corliss en- 
gine, and is a fair representation of diagrams fre- 
quently encountered and considered as a correct 
record of the action of the steam in the cylinder. 
The absence of data and atmospheric line renders 
the diagram worthless, except as an indication of the 
valve setting. But in this case the diagram is worth- 
less even for such a purpose, from the fact that the 
reducing motion was incorrect in every detail. At the 
point A the movement given to the paper barrel was 
too rapid, and the expansion curve is completed nearly 
in a straight line, while at other points the motion is 
correspondingly slower. To base any conclusions upon 
such a diagram is impossible, unless the error of the 



94 



Practical Application of the Indicator. 



reducing motion be known. This can readily be deter- 
mined, however, from the explanation given in Fig. 13. 




Indicator diagrams have many peculiar defects, 
and are due to several causes, chief of which are the 



Practical Application of the Indicator. 95 

engine, indicator and in many cases the man who 
manipulates the indicator. Frequently we hear en- 
gineers and manufacturers of indicators boast about 
their indicators taking such beautiful diagrams, but 
no engineer who understands the rudiments of his 
business will make or recognize any such claims. 
The value of an indicator depends upon its correct- 
ness and sensitiveness in responding to the most 
delicate variations in pressure, and the value of the 
diagram depends upon its correctness and not its 
beauty. Unless the utilization of steam by the en- 
gine is perfect (which case has never been found) 
the diagram cannot be perfect. 

Some engineers consider that the "how cheap" so- 
called indicators are good enough. But an inferior 
instrument is the poorest recommendation any en- 
gineer can offer, and we would advise all engineers to 
follow the good old rule that "the best is none too 
good and always the cheapest. " 

In the manner of attaching, ofttimes what is wrong 
is considered nearly correct, and what is nearly cor- 
rect is considered perfect, and the summing up 
amounts to a blunder that ends nowhere. A diagram 
is also frequently distorted by improper tension of the 
drum-spring, and in applying the pencil to the pap2r 
during more than one revolution it does not follow 
the same path of the admission line. 

The length of the diagram being nearly five inches 
is too long for a two-inch drum, unless the engine 
is running very slow. A more satisfactory result 
could be obtained with a four-inch diagram on slow 
speed engines. 



96 Practical Application of the Indicator. 

DIAGRAM FROM A MODERN CORLISS ENGINE SHOWING 
FAULTY CONSTRUCTION. 

Fig. 46 shows a diagram from a 32" x6o" Corliss 
engine. Revolutions, 56. The Corliss engine, as 
manufactured by the different builders, varies con- 
siderably in the economical utilization of steam, for 
which this style of engine has become so prominent. 
But like all other styles of engines they are more or 
less faulty in construction and must necessarily follow 




Fig. 46— Scale of Spring 40. 

with a corresponding loss of power and economy. 
The line A represents the pressure above the throttle 
valve and is the point from which the engine is re- 
sponsible for the loss of pressure at any point on the 
steam line. The loss of pressure at the commence- 
ment of the stroke is four pounds, and in some cases 
I have found a considerably greater loss, when it 
should have been only a fractional part of a pound. 
Frequently an engine may maintain nearly a straight 
steam line while the loss of pressure between the 
point above the throttle valve and cylinder may 



Practical Application of the Ifidicator. 97 

be considerable. At the point of cut-off, as shown 
by the dotted line, the pressure has fallen fifteen 
pounds. 

From time to time new styles of engines are put 
upon the market which we duly appreciate. But the 
majority of the present makes of engines are so defi- 
cient in the use of steam that if steps were first taken 
to bring this important factor to a degree of perfec- 
tion it would be a step in the right direction. 

If the Corliss engine be converted into a high- 
speed engine, the same as men frequently advocate, 
it would be simply a high-speed engine in nearly every 
sense of the word, and would lose all the advantages 
that the slow-speed and long-strok,e engine gains in 
economy above the high-speed and short-stroke, viz. : 
a high initial pressure is realized and maintained in 
the cylinder; the points of cut-off are better defined, 
which also causes less reduction in pressure. The ex- 
panding pressure can be maintained nearer full stroke 
and be properly released. The back pressure is less, 
and a lower cushion is necessary. The percentage of 
clearance is less, which also plays an important part. 



CHAPTER VIII. 

SETTING AUTOMATIC RIDING CUT - OFF VALVES WITH 
THE INDICATOR. 

While the riding cut-off engine, as manufactured 
by the different makers, also varies considerably in its 
details, a general understanding of the type as here 
illustrated and described and the method of adjust- 
ing, will enable anyone to readily adjust the valves 
on any of the different makes of this style of engine. 

Fig. 47 shows a central section through the cylin- 
der, valves and balance pistons. The left hand end 
being a section through one of the balance pistons I. 
The steam enters at D, through passages aa and bal- 
ance pistons to the interior chambers II of the valve, 
as shown by the arrows, in which the steam chest 
pressure is maintained. The balance pistons are 
packed with steam metal sprung rings between it and 
the followers F, thus preventing the steam from leak- 
ing out around the balance pistons into the exhaust 
K at the bottom and faced to work steam tight on 
the cover plate of the valve, also preventing the steam 
from leaking out between the face of balance piston 
and the face of cover plate. When steam is shut off 
from the engine the coiled steel springs E serve to 
hold the balance pistons and the main valve to their 
seats. The balance pistons have only the necessary 
area to hold the valves to their seats during admis- 
sion, and since the force of the balance pistons is con- 
stant, this force is too great after cut-off and during 

93 



Practical Application of the Indicator. 

Ei is?] aim mri 




Fig 47. 



100 Practical Application of the Indicator. 

release, and to counteract such excess, shallow re- 
cesses or relief chambers, as they are called, are 
formed in the valve seats corresponding to the cylin- 
der ports in shape and area, and are filled with ex- 
haust pressure, after which the steam chest pressure 
is admitted underneath the valve from the interior of 
the valve, through the small holes /, as shown near 
the crank end. This pressure is released into the ex- 
haust by the movement of the valve a trifle before the 
admission, as shown at the head end. Provision also 
is made to permit the main valve to raise from the 
seats and release any undue pressure that may accumu- 
late in the cylinder on the return stroke of the piston. 

Channels ee are cut across the valve faces near its 
ports which serve as passages into the exhaust for any 
steam that may accumulate under the valve through 
any imperfection of fit, which otherwise tend to throw 
the valve from the seats. These must be of sufficient 
capacity to permit the free escape of steam that may 
leak into them. Long wear reduces their depth and 
requires deepening or otherwise enlarging. 

Steam is admitted into the cylinder from the inter- 
ior of the valve, as shown by the arrow as just be- 
ginning to admit steam at the head end of the cylin- 
der and the main valve is also moving toward this 
end, while the other cylinder port is partly open for 
the exhaust, as shown by the arrow ; therefore the 
exhaust edges are at the ends of the valve and the 
steam edges near their inner margins. 

The cut-off valve is formed by two plates, shown 
at cc, rigidly connected by two rods and operated in- 
side of the main valve. 



Pi-actical Application of the Indicator. 101 

Fig. 48 shows the shaft governor. It belongs to 
that class of riding cut-off automatics in which the 
function of the governor is to move the loose eccen- 



Fig. 48. 



trie C forward on the engine shaft as the weights AA 
move outward by centrifugal force in opposition to 
the force of springs FF to the position as indicated 
by the dotted lines, near one of them, as the speed of 
the engine increases by the decreasing load. By this 



102 Practical Application of the Indicator. 

means in advancing the eccentric, it brings the cut-off 
valve around to meet the port of the main valve 
earlier, and the steam is cut off at an earlier point in 
the stroke. As the speed of the engine decreases by 
the increasing load the weights move inward and re- 
volve the eccentric backward, and the steam is cut 
off later. Arms aa are pivoted to the governor wheel 
at bb and connected at their other ends by links BB 
to ears on loose eccentric. 

To decrease the speed, more weight at AA is 
added, or the weights may be shifted farther outward 
on the arms, providing other parts do not interfere, 
and less tension is given to the springs FF which are 
adjusted by screws c c. To increase the speed, the 
adjustments are made vice versa. 

The amount of tension on the springs FF to give 
the closest possible regulation is determined by increas- 
ing their tension until the engine shows indication of 
racing, then the tension should be slightly lessened. 
When the tension of the springs is too great in the 
inner half of movement range as compared with the 
outer half, or, in other words, that the regulation of 
speed is less sensitive with light loads than heavy, 
the auxiliary springs are applied to assist in throw- 
ing the arms outward, leaving contact with the 
fingers at mid-stroke on which they act. The 
tension of FF must generally be about one-third 
to one-fourth greater than could be carried with- 
out them. If too great tension is given to the 
auxiliary springs they will start outward at a speed 
too much below the normal, or by too much loss 
of speed at heavy loads. 



Practical Application of the Indicator. 103 

The direction of motion is indicated by the arrow, 
and to reverse the engine, the arm as shown at the top, 
is removed to the unoccupied hole below it, and its 
side now shown, is turned toward the wheel. The 
other arm is removed to the unoccupied hole above in 
like manner, and the other parts are changed to cor- 
respond, so that the arrangement will correspond ex- 
actly with a view of the cut as it appears held up to 
a strong light and viewed from the back, or as it would 
in a looking glass. The positive eccentric is set to 
follow the crank with the same number of degrees on 
the other side of the crank, and the automatic eccen- 
tric C is set to correspond, by shifting the governor 
wheel around on the shaft. In the manner of adjust- 
ing with the indicator it is necessary that certain pre- 
liminary adjustments be made; first, that the rocker 
arm A which is carried by the positive eccentric, as 
shown in Fig. 49, to which the eccentric rod B is con- 
nected, shall be at right angles to the eccentric rod 
and vibrate to equal distances each side of a plumb line 
from its centre of vibration, when it is a horizontal 
engine and setting level. ■ This may be determined by 
the explanation previously given in Fig. 22, or the gov- 
ernor wheel and positive eccentric may be loosened 
and revolved on the shaft. The vibration of the rocker 
arm C of the automatic eccentric is determined in like 
manner, when the arm D is plumb and at right angles 
to the valve stem, and the arm C is at right angles to 
the inclined eccentric rod E. When it is a vertical 
engine and straight connected, the centre line of the 
rocker arm must be level at mid-stroke and at right 
angles to the rods. The remaining adjustments are 



104 Practical Application of the Indicator. 




Practical Application of the Indicator 



105 



made by use of the indicator; first, equalize the com- 
pression, admission and release on the main valve stem, 
which are all controlled by the main valve; and sup- 
posing a pair of diagrams be obtained, as shown in Fig. 
50. The compression and admission of the head end 




Fig. 50— Scale of Spring 40. 

are too early and the release too late. The crank end is 
vice versa; and since the compression and admission 
of the head end takes place by the movement of the 
valve toward this end and the release while the move- 
ment is toward the crank end, it is plain to be seen 
the valve stem of the main valve is too long and should 
be shortened until the compression, admission and re- 



106 Practical Application of the Indicator. 

lease are equal on both ends of the cylinder. Whether 
they are perfect, too early or too late, they should be 
equally so from both ends. 

Should a pair of diagrams be obtained as was 
shown in Fig. 27, where the compression, admission 
and release are late on both ends of the cylinder, it 
only requires to advance the positive eccentric until the 
admission lines are perpendicular and the compression 
and release will also be equal and perfect, providing 
the valve is properly constructed. But should the re- 
sults be too early, as was shown in Fig. 28, the eccen- 
tric should be set back accordingly. Sometimes with 
improperly constructed main valves, it is necessary to 
sacrifice a little of the perfect admission in order to 
obtain a satisfactory cushion. The cut-off is next 
equalized. This is accomplished by adjusting the valve 
stem of the cut-off valve. Should the cut-off on the 
crank end be the earliest, as was shown in Figs. 30 
and 31, and since the cut-off on the crank end of the 
cylinder takes place while the valve is moving toward 
this end, it is plain to be seen that the valve stem is 
too short and should be lengthened; and should the 
cut-off on the head end be the earliest, the valve 
stem should be shortened accordingly. 

The last adjustment to be made is to set the gov- 
ernor wheel, and it should have no more advance 
than is necessary to hold the engine to speed under its 
friction load and highest pressure. This is determined 
by placing the engine on either centre, mark the cross 
head and guide, then revolve the engine in the direc- 
tion of motion about J" travel on the crosshead. But 
this depends principally upon the amount of friction 



Practical Application of the Indicator. 107 

and size of engine, pressure and tightness of piston 
and valves, and with the weights AA blocked to their 
outward movement to the position indicated by the 
dotted lines near one of them, set the governor wheel 
so that the cut-off valve is just beginning to close the 
port of the main valve. To test the adjustment, run 
the engine with its friction load and highest pressure, 
and should the speed increase considerably above the 
normal, advance the governor wheel accordingly. 

From these explanations it can readily be seen 
that the manner of adjusting riding cut-off valves with 
the indicator is not so intricate as generally sup- 
posed, but is really a very simple undertaking when 
thoroughly understood. 

DIAGRAMS FROM AN ENGINE ON WHICH AN INDICATOR 
HAD NOT BEEN USED FOR ELEVEN YEARS. 

Fig. 51 shows a pair of diagrams from a i6 ff X32" 
automatic riding cut-off engine. Diameter piston 
rod, 2\" ) revolutions, 93. This engine was erected 
eleven years ago, at which time the valves were ad- 
justed with the indicator, and since then no re-adjust- 
ments have been made. The unequal distribution of 
steam is caused by the valve being out of its proper 
position, which no doubt was caused by frequent key- 
ing up. The head end exhaust edge closes too early, 
causing a too high Compression, and a too early ad- 
mission follows. The full pressure is admitted into 
the cylinder before the piston has completed the 
stroke, as shown by the admission line leaning out- 
ward, consequently the pressure in the cylinder must 
be forced back into the steam chest as the piston 



108 



Practical Application of the Indicator. 



completes the stroke. When the piston has com- 
pleted the stroke the pressure in the clearance space 
and steam chest equalize and the pencil falls, caus- 
ing a peak above the diagram as shown. The com- 




Fig. 51— Scale of Spring 40. 



pression is the highest pressure compressed in the 
clearance space; therefore, the compression in this 
case is measured at the highest point at the com- 
mencement of the diagram, which is 74^ pounds, and 
at this time there is a partial vacuum of 5 pounds on 



Practical Application of the Indicator. 109 1 

the other side of the piston, which is measured on 
the crank end diagram near the termination of the 
expansion curve; therefore, the cushion is yg\ pounds 
and is the highest unbalanced pressure realized on 
the piston at the instant it comes to a standstill. 
This will more than stop the piston before the end of 
the stroke, and were it not for the energy stored in 
the fly wheel the engine would stop. Considering 
the length of stroke, speed and character of the com- 
pression curve about 15 or 20 pounds cushion should 
be sufficient to secure smooth running. 

The crank end diagram has no steam line because 
the cut-off took place before the piston had made any 
movement. The highest pressure realized at this end 
is only 70 pounds, as the cut-off took place even before 
the full pressure was realized in the clearance space. 
The admission is too late, as shown by the admission 
line leaning slightly inward. The compression rises 
more rapidly than on the head end, because the piston 
approaches nearer the crank end, due to the clearance 
being unequally divided. The compression curve, at 
the point where it intersects with the admission line 
goes out partly in a straight line and is caused by 
condensation because the temperature of this end of 
the cylinder is lower than the temperature of the 
compression. When the expansion curve reaches the 
back pressure line the piston has only moved about 
one-third of its stroke and the pressure is balanced 
on both sides of the piston, and were it not for the 
motion of the fly wheel and reciprocating parts the 
engine would stop at this point of the stroke. As the 
piston completes the stroke the expansion curve con- 



110 Practical Application of the Indicator. 

tinues to fall below the atmospheric line, causing a 
partial vacuum on the admission side of the piston 
and the fly wheel and reciprocating parts must force 
the remaining stroke of the piston against a pressure 
equal to the vacuum formed on this side of the piston, 
plus the back pressure, above the atmospheric on the 
exhausting side. 

The loop embraces the greater part of the diagram, 
consequently the countermotion is greater than the 
load carried by the steam, hence it takes power from 
the head end to drive the crank end. The unequal 
distribution of steam on each side of the piston caused 
considerable variation of speed during each revolu- 
tion and the belt was constantly whipping. 

DIAGRAMS SHOWING INCORRECT ADJUSTMENTS. 

Fig. 52 shows a pair of diagrams from a I2"x24", 
riding cut-off automatic engine. Revolutions, 104. 
These diagrams show the manner in which the builder 
adjusted the valves with the indicator. The adjust- 
ments are incorrect and the distribution of steam on 
each side of the piston is unequal. The compression is 
too high and follows with a too early admission, and 
the full pressure is admitted into the cylinder before 
the piston has completed the stroke. The compres- 
sion and admission take place on the head end still 
earlier than the crank end, therefore the stem of the 
main valve should be shortened and the positive ec- 
centric set back until the admission lines are per- 
pendicular, which will cause a later closing of the 
exhaust valves and a lower cushion. The cut-off on 
the crank end is the earlier, therefore, the stem of 



Practical Application of the Indicator. 



Ill 



the cut-off valve should be lengthened, but owing 
to the fact that the position of the positive ec- 
centric must be changed, the governor wheel of the 




automatic eccentric must be set to correspond. 
The compression of the head end is 59 pounds 
and the counter-pressure is one pound, thus giving 
58 pounds cushion. The cushion of the crank end 
is 56 pounds. 



112 Practical Application of the Indicator. 

SETTING AUTOMATIC RIDING CUT-OFF VALVES BY THE 
SOUND OF THE EXHAUST. 

Fig. 53 shows a pair of diagrams from a i6 ff X34 r 
automatic riding cut-off engine, revolutions 100. 
The valves were set by the sound of the exhaust, 
and because the engine runs smooth as indicated by 
a sufficient cushion, the owner thought that the 
valves had been properly adjusted, but when the 
fuel bills increased and the engine became unable to 
carry the load, it was a sticker in his mind and he 
was forced to search for the truth. Without any 
further guesswork he called in the man with the indi- 
cator, who upon inspecting the diagrams saw at a 
glance that the difficulty could not be remedied by 
any adjustments on the outside of the engine. Had 
the main valve stem been lengthened so as to make 
the admission lines equally late on both ends it would 
necessitate a considerable advancing of the eccentric 
in order to obtain a proper admission, which would 
cause a too high cushion. The steam chest cover 
was taken off and the valve is formed of two plates 
and connected by rods. It was found that the head 
end plate had been moved toward the crank end, and 
since the valve admits steam while moving away from 
the crank end, it is plain to be seen that this caused 
the late admission on the head end. When the pis- 
ton commenced its stroke at the head end the steam 
valve at first remained closed, the admission line fell 
below the compression curve until the piston had 
moved a considerable distance, when the steam valve 
opened and raised the pressure, thus forming the 
loop. But since the piston had moved such a con- 



Practical Application of the Indicator. 



113 



siderable distance before the admission commenced, 
it caused an undue loss of admission pressure. The 




long compression curves indicate excessive clearance 
or leakage out of the cylinder, which is shown in 
the crank end compression curve. 



CHAPTER IX. 

SETTING SINGLE VALVE AUTOMATICS WITH THE 
INDICATOR. 

While the single valve automatic engines as manu- 
factured by the different makers also vary consider- 
ably in their details, a general understanding of the 
type as here illustrated and described, and the 
method of adjusting them with the indicator, will 
enable anyone to readily adjust the valves on any of 
the different makes of this style of engine. The dif- 
ference in adjusting depends chiefly upon whether 
the valve admits steam into the cylinder from the 
center of the valve or at the ends. With valves ad- 
mitting steam from their ends the eccentric leads the 
crank, and while the piston is moving rapidly the 
valve is moving slowly, and vice versa, due to the 
angularity of the connecting and eccentric rod, which 
is well understood by all engineers familiar with the 
mathematics of the steam engine. This objectionable 
feature is obviated by admitting steam into the cylin- 
der from the inner margins of the valve and the 
eccentric follows the crank, which causes the piston 
and valve to move in unison. 

Fig. 54 shows a central section through the cylin- 
der, steam chest and the right end of the valve; 
the other end being a section through the valve. 
The steam chest pressure surrounds the valve, and as 
it is moving toward the head end, the live steam edge 

114 



Practical Application of the Indicator. 



115 



of the valve is shown by the lower arrow as just 
beginning to admit steam into the head end of the 
cylinder, another passage being in a port at the other 
end of the valve and through the tubing, as indicated 
by the course of arrows, thus forming a double port 
valve. The steam is exhausted at the other end of 




Fig. 5i. 

the valve, and when the piston is at the crank end 
the valve is also in the opposite direction. 

Fig. 55 shows the shaft governor. It belongs to 
that class of single valve automatics in which the 
function of the governor is to move the eccentric 
across the engine shaft, altering its throw and vary- 
ing the travel of the valve, either by changes of load 
or changes of steam pressure. It consists essentially 
•of a governor wheel which is fixed on the engine 



116 



Practical Applicatio?i of the Indicator. 



shaft, to which are hinged the weights, i, I. These 
weights are moved outward by centrifugal force in 
opposition to the springs. The inner eccentric, C, 
having ears attached and connected with the weights 
by rods, 2, 2. The outer eccentric ring, D, is free to 




Fig. 55. 

turn on the outside of the inner eccentric, and is con- 
nected to the toe of one of the weights by rod, 3. 

On this outer eccentric ring is placed the usual ec- 
centric strap (which is not shown in the cut) to which 
the eccentric rod is connected. When the engine has 
its greatest load the weights will be in the inner posi- 
tion, as shown in the accompanying cut; and the 
throw of the eccentric will be the greatest, conse- 



Practical Application of the Indicator. 



117 



quently the valve must return to cut-off correspond- 
ingly later. The eccentricity of the two combined 
eccentrics is then the distance, as shown at B. As 
the speed of the engine increases, by the decreasing 
load, the weights overcoming the springs move out- 




Fig. 56. 

ward, which decreases the travel of the valve and the 
steam is cut off earlier. When the weights are in the 
extreme outer position, as shown in Fig. 56, the point 
of cut-off should be sufficiently early so that the speed 
of the engine does not materially exceed the normal 
with the friction load and highest steam pressure. 
The eccentricity of the two combined eccentrics is 
then the distance shown at A. 



118 Practical Application of the Indicator. 

The manner of changing the speed and direction of 
motion will be about the same as was explained in Fig. 
48. But in some types of governors it is necessary to 
use parts differently constructed. An engine that is 
equipped with a shaft governor not contained in the 
fly wheel is, of course, more convenient for altering 
the valves, as the eccentric can readily be changed to 
any position so as to obtain the proper action of the 
valve under various conditions, according to the engi- 
neer's own fancy. Such a device any intelligent 
engineer cannot fail to appreciate. However, with 
nearly all governors that are contained in the fly- 
wheel it is necessary to change the position of the fly- 
wheel on the engine shaft in order to alter the valve. 

When single valve engines are equipped with a 
rocker arm it is necessary that it shall have the proper 
vibration, as explained in Fig. 22. The remaining 
adjustments are made by the use of the indicator. 
First, the load or steam pressure, or both, should be 
varied so the cut-off on both ends of the cylinder will 
average about one-quarter, which is about the center 
of distribution in a single valve automatic engine, and 
the cut-off varies unequally from this point, due to 
the angularity of the eccentric rod. Supposing a pair 
of diagrams be obtained, as shown in Fig. 57, the 
head end exhaust closure and lead is too early and 
the cut-off and release too late. The crank end is 
vice versa, and since the compression, admission, cut- 
off and release are all controlled by the same valve, and 
the compression and admission take place at the head 
end, while the movement of the valve is toward the 
head end, and the cut-off and release while the valve 



Practical Application of the Indicator. 



119 



is returning, it is plain to be seen that the valve stem 
is too long and should be shortened until the results 
be equal on both sides of the piston. Whether they 
are too early or too late they should be equally so on 
both ends. Should the crank end compression and 
admission be too early and the cut-off and release too 
late, the valve stem should be lengthened accordingly. 
Should the results then be too late, as shown in Fig. 




Fig. 57— Scale of Spring 40. 

27, the eccentric should be advanced, and if too early, 
as shown in Fig. 28, the eccentric should be set back 
accordingly. 

It frequently happens that it is necessary to sacri- 
fice the accuracy of one of the main functions, either 
compression, admission, cut-off or release, in order to 
accommodate the other three, but when the engine 
is overloaded it is then necessary to make up the 
deficiency in cushion with live steam. 



123 Practical Application of the Indicator. 

AN EXCELLENT DIAGRAM FROM A MODERN HIGH-SPEED 
ENGINE. 

Fig. 58 shows a diagram taken from a 1 5 J ;/ X 1 5 " 
single valve automatic engine. Revolutions, 250. 
This cut gives the general features of a well-formed 
indicator diagram of a high-speed engine, and one of 
the most beautifully formed steam lines that scientific 
steam engineering can produce. The maintenance of 
such an absolutely straight steam line to the absolute 
point of cut-off is the most difficult feature to produce 




Fig. 58— Scale of Spring 50. 

in a high-speed engine. This is accomplished in this 
engine to the highest degree of perfection. The ad- 
mission pressure approaches the pressure above the 
throttle valve to a fractional part of a pound, and 
unless all other engine builders can match it in as 
perfect a utilization x)f steam, they must necessarily 
follow, taking this figure as an example to imitate, 
while endeavoring to produce an engine that may be 
of modern character. The point of cut-off embraces 
an equal degree of perfection, and is defined with the 
utmost rapidity. The expansion and compression 
curves are wavy, caused by fluctuation in pressure 



Practical Application of the Indicator. 121 

and oscillations of the indicator piston. The admis- 
sion line also has its beauty as the full pressure was 
admitted into the clearance space at the instant the 
crank was passing the dead center, and this rapid ad- 
mission caused the pressure to fluctuate above the 
normal and caused the peak above the diagram. The 
undue back pressure is caused by restricted area 
through the exhaust pipe. This diagram will bear a 
great deal of study by all engineers, especially those 
in charge of high-speed engines, where the diagrams 
depart from the prominent features as attained in this 
diagram. However, the engine is overloaded, and to 
obtain better economy and carry the same load the 
boiler pressure should be increased which would re- 
sult in an earlier cut-off and a lower release pressure. 
If engineers will compare the absolute efficiency 
of different styles of engines in an accurate manner, 
it will prove a revelation that will force them to 
.acknowledge that many of the so-called high grade 
engines are so deficient in the utilization of steam 
that they never should have been recognized as a 
modern steam engine. 

A DIAGRAM FROM A MODERN HIGH-SPEED ENGINE, 
SHOWING FAULTY CONSTRUCTION. 

Fig. 59 shows a pair of diagrams from a io"xi2", 
single valve automatic engine. Revolutions, 255. 
These diagrams were taken after the valve was ad- 
justed by the builders, and it proves whether or not 
the engine is capable of the proper performance so as 
to bear them out in their claims. The diagrams show 
that the adjustments were judiciously made, as the 



122 Practical Application of the Indicator. 

four points are fairly equal — namely, the admission, 
cut-off, release and compression, and these features 
being accomplished the builders considered that they 
had a novel result. But these diagrams, upon inspec- 
tion by a "card sharp," only proves what I have 
already stated, viz., the majority of engine builders 
are not as close readers of indicator diagrams as they 
are generally credited with being; and unless they are 
proficient in the application of the indicator and the 
close observers of the diagrams, it must necessarily 
follow that their engine is as deficient as the conclu- 




Fig. 59— Scale of Spring 40. 



sions based upon the diagrams. This is self-evident,, 
when it is considered that in these diagrams all the 
prominent features that were attained in Fig. 58 are 
lacking. By a comparison of the difference of effi- 
ciency of the two diagrams mentioned it should be 
sufficient evidence for engineers that such engines 
should never be placed in the field where fuel, boiler 
capacity, etc., is of any value without any ifs, ands, 
or buts. The steam pressure from above the throttle 
valve, not being known, the loss of pressure at any 
point on the steam line can only be calculated from 
the initial pressure line A A, which line is located by 
measurement on the scale of the spring at such a dis- 



Practical Application of the Indicator, 123 

tance above the atmosphere line, as is represented 
by the initial pressure. Had the pressure above the 
throttle valve been known, and should have been 
taken with another instrument at the same time 
the cylinder diagrams were taken, this loss of pres- 
sure could be accurately determined. At the point 
represented by the first dotted line the steam valve 
commences to close and the pressure has fallen 1 5 
pounds below the initial pressure. The valve has 
not fairly closed until at the point shown by the 
second dotted line because the expansion curve at 
this point changes from convex to concave, and 
the loss of pressure is 20 pounds, and there is 
about an equal loss of pressure at the other end 
of the cylinder. 

This great loss of pressure during admission gen- 
erally follows with a serious loss of pressure between 
the highest pressure realized in the cylinder and that 
above the throttle valve and is a corresponding loss 
of power and economy. This is only one of the many 
objectionable features that cause steam users to dis- 
cover why they lack boiler and engine capacity when, 
according to the engine builder's rating, the engine 
should be more than ample. The exhaust valves 
open and release the pressure before the point of 
release on the diagrams meet with the compression 
curve and is a too early release. 

The ports were very long and indirect, causing a 
large per cent of clearance which also is an object- 
ionable feature, and is shown by an early exhaust 
closure in order to produce the necessary cushion. 
The admission is too early, as shown by the admission 



124 Practical Application of the Indicator. 

lines leaning outward causing the peak above the dia- 
grams, which, however, are common with high speed 
engines. This, however, may be intentional so that 
the valve may be more open, so as to better maintain 
the pressure when the movement of the piston com- 
mences. 

A considerable less pressure is realized on the 
head end which may be accounted for from the 
fact that when the movement of the piston was 
rapid the movement of the valve was slow, and vice 
versa, because the valve admitted steam" at the ends 
of the valve. 

This faulty construction is not confined to a single 
make of engine but is found in many single valve 
engines, and the manufacturers of such engines 
should make the necessary changes. 

SETTING SINGLE VALVE AUTOMATICS BY THE SOUND 
OF THE EXHAUST. 

Fig. 60 shows a pair of diagrams from a 10" X 12" 
single valve automatic engine. Revolutions 285. The 
valve of this engine was set by the sound of the ex- 
haust and judging from the diagrams the man who 
followed this method of setting engine valves displayed 
his ignorance. In this case the sound of the exhaust 
was equal from the fact that the head end was ex- 
hausting no pressure as shown by the expansion curve 
crossing the atmospheric line before the end of the 
stroke. The crank end exhaust valve closes too early 
and forms J J pounds compression, thus exceeding the 
steam chest pressure, and when the steam valve opens, 
the pressure passes into the steam chest and the pen- 



Practical Application of the Indicator. 125 

cil falls, causing the loop above the diagram. The 
steam valve closes at a late point in the stroke and 
the pressure is 22 pounds when it is released. The 
head end steam valve remains closed and the pressure 
in the expansion curve is produced by the compression 
and the leakage of steam into the cylinder. The 
loops at each end are nearly as great as the. other 
portion of the diagram and, were it not for the leakage 
of steam into the cylinder, it would require power 




Fig. 60— Scale of Spkimg 46. - 

from the crank end in order to drive the head end. 
The valve admitted steam at the ends of the valve 
therefore the first adjustment made was to shorten 
the valve stem. The amount saved in fuel in a few 
days only, more than paid the cost of adjusting with 
the indicator, but many of the owners of steam-plants 
are ignorant as to the economical utilization of steam 
in an engine and not until they are forced to do so 
will they go to the expense of having the engine 
properly adjusted with the indicator. 



126 



Practical Application of the Indicator. 



Fig. 6 1 is another example of setting single valve 
automatics by the sound of the exhaust and is taken 
from a io"XI2" single valve engine. Revolutions 250. 
The crank end in this case is exhausting no pressure. 
The exhaust valve closes and forms the compression 
but the steam valves does not open in due time and 
when the piston commences to move away, the press- 
ure falls and forms the loop at the commencement of 





Fig. 61— Scale of Spring 30 

the diagram. The steam valve th^en opens a trifle 
and raises the pressure but is immediately' closed and 
the expansion curve crosses the back pressure line at 
an early point in the stroke and should have ex- 
panded below the atmospheric line and its failure to 
do this indicates leakage of steam into the cylinder. 
The head and exhaust valve closes too early and 
the compression rises above the steam chest pressure 
and when the steam valve opens the compression and 
the steam chest pressure equalize and form the loop. 



Practical Application of the Indicator 



127 



A DISTORTED DIAGRAM CAUSED BY INSUFFICIENT 
TENSION OF THE DRUM-SPRING. 

Fig. 62 shows a diagram from an 8"Xio single 
valve automatic engine. Revolutions 336. The dia- 
gram shows that the drum-spring of the indicator had 
insufficient tension and produced a fling at the end of 
the stroke as shown by the admission lines not merging 
into each other. If the pencil be applied during 
several revolutions and the admission line is broader 
than the width of a single pencil mark, it indicates a 
defect in the indicator, or reducing motion, due to 




Fig. 62— Scale of Spring 60. 

vibration of the reducing motion, cord stretching, or 
improper tension of the drum-spring. The load of 
this engine varied suddenly and the pencil was applied 
during one revolution with the heaviest load, as shown 
by the late cut off, and another revolution when the 
load was thrown off leaving only the friction load of 
the engine and machinery as shown by the early point 
of cut-off. This decrease in load increased the speed 
and caused a greater fling of the drum. The steam 
valve closed before the full pressure was admitted into 
the cylinder and reduced to initial pressure. With 



1 28 Practical Application of the Indicator. 

such a pressure of steam and early point of cut-off the 
expansion curve should fall below the atmospheric 
line, and its failure to do this indicates a leak in the 
steam valve. 

It will be seen that with a single valve automatic 
engine, as the load decreases the cut-off, release and 
exhaust closure take place at an earlier point in the 
stroke, while the lead should remain constant. 

The compression shown in the diagram with the 
heavy load, as indicated by the late point of cut-off, 
is only 23 pounds, and since the late point of cut-off 
causes a higher counter-pressure and the late exhaust 
closing causes a lower compression, the cushion is 
rapidly reduced. 

This is one of the most objectionable features in a 
single valve automatic engine of this type from the 
fact that the valve travel is varied by altering the 
throw of the eccentric which is moved across the en- 
gine shaft, due to the changes of load or changes in 
pressure of steam. As the load decreases the valve 
travel also decreases and the admission and exhaust 
are cut off at an earlier point in the stroke. 

The compression in the diagram representing the 
early point of cut-off increases to 41 pounds while at 
the same time the counter-pressure decreases and the 
cushion increases rapidly. 

Where the exhaust is controlled with a positive 
eccentric, the compression should practically remain 
constant and the cushion is only affected by the 
change in the counter-pressure caused by the variation 
in the point of cut-off due to changes in load or 
changes in steam pressure. 



Practical Application of the Indicator. 



129 



One of the admission lines lean slightly inward 
and indicates a trifle late admission. The peak at 
the top of one of the admission lines which extends 
above the steam line is caused by a fling of the pencil. 

DIAGRAMS FROM AN OVERLOADED HIGH SPEED ENGINE. 





Fig. 63— Scale or Spring 60. 

Fig. 63 shows a pair of diagrams from a 10" X 12" 
single valve automatic engine, revolutions 283. This 
engine was runnning noisy and needed to be fre- 
quently repaired. The diagrams show that the high 
terminal pressure destroyed the cushion which caused 
the trouble. If the eccentric had been advanced, 
the lack in cushion would have been obtained by ad- 
9 



130 



Practical Application of the Indicator. 



mitting live steam into the cylinder before the pis- 
ton completed the stroke and the admission lines 
would lean outward. The engine is overloaded to 
the limit and should be replaced with one of proper 
size, which would effect a saving in fuel sufficient to 
pay for the engine in a short time. The irregularities 
in the steam lines are caused by oscillations of the 
indicator piston, due to the rapid admission of steam 
and high speed, and a spring of higher tension 




Fig. 64— Scale op Spring 40. 

should have been used. The initial pressure in this 
case is measured from the atmospheric line to a point 
so that at an average height the oscillations are as 
much above as below. 



DIAGRAMS FROM EACH END OF THE CYLINDER, SHOW- 
ING A DIFFERENCE IN THE INITIAL PRESSURE. 

Fig. 64 shows a pair of diagrams from a I i ;/ X 16" 
single valve automatic engine, revolutions 175. The 
initial pressure on the head end is less than on the 
crank end, and is caused by the valve admitting steam 
from the ends, in which case while the piston is mov- 



Practical Application of the Iiidicator. 131 

ing rapidly on the head end the valve is moving 
slowly, and vice versa. Had the valve admitted 
steam from the inner margins the piston and valve 
would have moved in better unison. 

The points of cut-off are poorly defined, caused 
by the valve being slow in its action while closing, 
and is a loss in power and economy. 

-SERRATED CURVES CAUSED BY UNEQUAL EXPANSION 
OF THE INDICATOR-PISTON AND CYLINDER. 

While an indicator may be free from friction when 




Fig. Go— Scale of Spring 60. 

cold, as explained in the chapter on "The Indicator," 
nevertheless, when in contact with steam, it may be 
subject to undue friction, due to unequal expansion 
of the piston and cylinder, and the expansion and 
compression curves will be serrated, as shown in 
Fig. 65. This can readily be tested by detaching 
the spring, and with piston attached raise the piston 
to its highest position with the pencil motion, and 
in this position admit steam, and when well heated 
shut off steam, and immediately commence to raise 
and lower the pencil motion to its highest and low- 
est positions, and if there is a suspicion of a catch 



132 Practical Application of the Indicator. 

it is due to this cause. But if slight it may be 
remedied by inserting a spring of such tension that 
the piston moves through the entire range of its mo- 
tion and attaching the indicator to one end of the cyl- 
inder, but without attaching the paper-drum to the 
reducing motion allow the piston to work in commu- 
nication with the steam in the cylinder a few hours. 
Should this fail to remove the defect the instru- 
ment is impracticable and should not be used. If 
engineers will submit the different makes of indi- 
cators that they may come in contact with to these 
simple tests, and as they become skilled in the im- 
portance depending upon this indispensable instru- 
ment, they will indorse the statements which I have 
heretofore made against inferior makes of indicators, 
and agree as men of science that there is want 
of a more correct instrument than exists, even 
among the best makes. 

THROTTLING OR SLIDE VALVE ENGINE. 

The throttling or commonly called the slide-valve 
engine, usually admits steam at the ends of the valve, 
otherwise the manner of equalizing the four points, 
namely, the admission, cut-off, release and com- 
pression are the same as the single valve automatic 
explained in Fig. 57, except that the load or steam 
pressure need not be varied. This valve is operated 
with a positive eccentric, and its movement is con- 
stant. Advancing, the eccentric brings these four 
points earlier, and vice versa. The governor is placed 
in the steam pipe and its function is to throttle the 
pressure accordingly as the speed of the engine in- 



Practical Application of the Indicator. 133 

creases or decreases above the normal by the varia- 
tion in load, and is called a throttling governor. It 
is simply a choker in the steam pipe, and such ancient 
and wasteful method of working steam should make 
a scrap-pile blush with shame. 

It is frequently assumed that steam plants equip- 
ped with slide valve engines in localities where fuel is 
free of cost, are the proper type of engines to use, 
and the plant can be installed at a less cost. This is 
merely supposition and ignorance, as such plants are 
the most costly in price, first, last and always, for the 




Fig. 66— Scale of Spring 40. 

simpie reason that it requires about double the boiler 
capacity, and this additional expense, together with 
the extra cost for attendants, repairs etc., will more 
than balance the lesser price of the slide-valve engine 
as compared with any high grade automatic. 

Fig. 66 shows the general features of a well 
formed diagram from a throttling engine, the attain- 
ment of which should be the aim in setting this valve. 
The release and compression are perfect, the back 
pressure line merges into the atmospheric line. The 
steam lines are maintained in straight lines and the 
points of cut-off which usually take place about | 



134 



Practical Application of the Indicator. 



stroke in a throttling engine are well defined. The 
three steam lines at different heights show the action 
of the governor under variations in load, while in 
the automatic engines the full pressure is admitted 
and cut-off at a distance in the stroke, according to 
the load, as shown in Fig. 31. 

TYPICAL COMPRESSION CURVES AND ADMISSION LINES. 

The compression curves a, b, c, as shown in Fig. 
67, while differently formed, are all caused by more 





Fig. 



or less leak in the exhaust valves or piston; a is sub- 
ject to a greater leak than -b, while b also may be 
caused by a high compression whose temperature 
exceeds the temperature of the interior of the cylin- 
der when condensation takes place and is completed 
in a partly straight line. 

Long service will cause the valves in a Corliss 
engine to wear that portion of the chambers in which 
it moves, and if the valve rods are altered, the leak- 
age will be greater when the valves rise upon the 
shoulder, while the valves may be tight when moving 



Practical Application of the Indicator. 



135 



in its former position. This leak may more than 
balance the advantages for which the alterations were 
made, and the chambers should be rebored and the 
valves replaced with correspondingly larger ones. 

If the compression curves indicate leak only at 
one end of the cylinder; it is generally caused by the 
exhaust valve, while if at both ends, it may be the 
piston, or both. 

d has no compression, because the exhaust valve 
remains open until at the end of the stroke, and the 




Fig. 68. 



back pressure line is completed in a straight line, e 
has too high compression, because the exhaust valve 
closes too early and the compression exceeds the 
steam chest pressure, and when the steam valve 
opens, the pressures equalize and form the loop. 

The admission line a, as shown in Fig. 68, leans 
outward and indicates a too early admission, and a 
peak is formed above the steam line as shown. Fre- 
quently a peak is formed as shown at b, yet the ad- 
mission line is perpendicular and is caused by a fling 
of the pencil motion, which in turn is caused by 



136 Practical Application of the Indicator 

momentum of the indicator piston. It also may be 
caused by rapid opening of the steam valve, which 
causes fluctuation in pressure. 

c leans inward and indicates a too late admis- 
sion ; d is first too early and then too late, and is 
accounted for by an improper movement in the open- 
ing of the valve. This frequently happens with a 
Corliss engine in keying up the connections in the 
hook and eccentric rods when the vibration of the 
rocker arm becomes unequal, or in any other type of 
engine that is equipped with a rocker arm. In e, the 
steam valve remains closed at the commencement 
of the stroke and the pressure falls, forming the loop. 
f indicates no compression and late admission which 
may be caused by the exhaust valve being open when 
the entering steam blows into the exhaust and follows 
with loss of initial pressure. 

g has no compression. At the end of the stroke 
the exhaust valve closes and the steam valve also 
remains closed at the commencement of the stroke, 
and as the piston moves away it creates a vacuum in 
the cylinder, but when the steam valve opens the 
pressure rises and forms the loop. 

DEFECTIVE STEAM LINES. 

The defects in steam lines are due to several 
causes, chief of which are the indicator, improper 
movement of the steam valves during admission, 
leaky piston and exhaust valves, restricted area in 
the steam pipe, throttle valve, steam chests or ports. 
'Some of the peculiar defects frequently encountered, 
are often regarded as a mystery, but can readily be 



Practical Application of the Indicator 



137 



accounted for and remedied when properly traced 
with the indicator. 

The line A as shown in Fig. 69 shows a defect fre- 
quently found, especially in slow speed engines and is 
generally caused by leakage of pressure out of the 
cylinder. It will be seen that the pressure falls rap- 
idly at the instant the piston commences its stroke 
and is caused by leakage of pressure out of the cylin- 
der, but soon rises and restores the pressure equal to 



V 



B 



Fig. 69— Scale of Spuing 40. 



the pressure at the commencement of the stroke which 
is accounted for by the fact that the steam valve at 
this point in the stroke is fully opened, and since the 
piston has only moved a short distance, the volume is 
comparatively small and requires a less quantity of 
steam to raise the pressure. Had this loss in pressure 
taken place at a later point in the stroke, when the 
volume would be greater, it would require a greater 
quantity of steam in order to restore the pressure and 
unless the engine is running slow the pressure could 



138 Practical Application of the Indicator. 

but slowly raise and would cause a corresponding 
lower pressure. But, however, many of the indicator 
diagrams showing defects, are a false record of the 
action of the steam, and may be attributed to an 
inferior instrument or improper application of the in- 
dicator, or both. 

The steam line B has two points of cut-off and 
some of the reasons frequently given for this are oft- 
times amusing. While some of these wildcat ideas 
may be the case, nevertheless, the general cause is 
due to the fact that in a slow speed engine, equipped 
with a shaft governor, and especially those having a 
light fly-wheel, and a short valve travel, in which case 
the governor needs only to slightly alter its position 
in order to vary the point of cut-off, and frequently 
causes a re-opening of the steam valve, making two 
points of cut-off. In this case, the engine had a light 
load as shown by the first point of cut-off but when 
the piston had moved only a short distance, an excess- 
ive load was suddenly applied which reduced the 
speed and the governor being sensitive in its action, 
instantly re-opened the valve causing the second ad- 
mission, but owing to the fact that the piston had 
already moved a considerable distance, the pressure 
could not be restored equal to the first time of ad- 
mission. 



CHAPTER X. 

ANALYSIS OF BOILER FEED PUMP DIAGRAMS. 

The maintenance of an economical utilization of 
steam in pumps is no less an important factor than 
a properly constructed pump, which fact has been 
greatly neglected by nearly all engineers. The indi- 
cator should be applied to the steam and water cylin- 
ders of every pump in order to determine that the 
plunger and valves are free from leaks, and that the 
speed of the pump does not exceed the capacity of 
the suction and discharge passages, so as to create un- 
due suction and discharge pressure in the water cylin- 
der. The length of strokes should not vary and the 
steam piston should approach the ends of the cylin- 
der as nearly as possible ; the ports should be short 
and direct, so as to reduce the percentage of clearance 
to a minimum, because the steam in the clearance 
spacein a pump is a total loss on account of there being 
no expansion. The water cylinders of all pumps are 
subject to leakage and they ofttimes lack capacity 
which could be traced with the indicator and rem- 
edied, when their capacity would be more than ample. 

Fig. 70 shows the general features of a well formed 
diagram from the steam cylinder. The exhaust 
valve closes just in time to prevent the entering steam 
from passing into the exhaust, as shown by the slight 
compression curve at the left hand end of the diagram ; 
and before the piston completes the stroke the steam 

139 



140 Practical Application of the Indicator. 

valve opens and stops the piston with live steam, so 
as to prevent it from striking the head, as shown by 
the admission line leaning outward. With higher 
speed the piston moves further before it can be 
stopped, and this increase of stroke causes the ad- 
mission line to lean outward still more. 

The steam line is straight and parallel with the 
atmospheric line which indicates a uniform piston 
speed, which otherwise would be wavy. 

The release line as shown at the right hand end of 
the diagram is perpendicular, and the exhaust pres- 



Fig. 70— Scale of Spring 40. 



sure is reduced to a minimum before the piston be- 
gins to return. The back pressure line merges into 
the atmospheric line, which shows that the exhaust 
passages are ample for the speed. 

Fig. y I shows the general features of a well formed 
diagram from the water cylinder. The line A is the. 
atmospheric line from which the discharge and sup- 
ply pressure above, and suction below is measured. 
The lower line is the suction line. The suction is 
measured on the scale of the spring from the suction 
line to the atmospheric line, and represents by its 
distance below the atmospheric line, the height the 



Practical Application of the Indicator. 141 

water is lifted, resistance in passing through the suc- 
tion pipe, ports, and the pressure necessary to raise 
the discharge valves. If the suction passages are 
ample for the speed, the suction line will be main- 
tained in a straight line, and only the necessary dis- 
tance below the atmospheric line to accomplish this 
result with freedom. When the water is supplied by 
pressure, this line will be elevated above the atmos- 
pheric line, and is then called the supply line, and 




Fig. 71— Scale of Spkin 



represents by its distance above the atmospheric line 
the pressure at which the water enters the cylinder. 
The loss of pressure through the supply passages 
should not be greater than is necessary for the free 
passage of the water to the cylinder, because with 
the least amount of suction (when the water is lifted) 
or the greater distance the supply line is elevated 
above the atmospheric line (when the water is sup- 
plied by pressure), the greater will be the gain in 
power and economy. 



142 Practical Application of the Indicator. 

When the plunger has completed the stroke, and 
if the cylinder is filled with water, and there be no 
leakage in the plunger, valves and discharge passages, 
the compression line as shown at the left hand end 
of the diagram will erect perpendicular when the 
plunger returns, because water practically, cannot be 
compressed nor expanded. 

The upper line is the discharge line, and if the 
discharge passages are ample for the speed, this pres- 
sure line should not exceed the boiler pressure or any 
other point of discharge more than is necessary to 
raise the valves and resistance through the passages, 
in which case the steam gauge and indicator must 
agree, and this line should be maintained in a straight 
line and parallel with the atmospheric line. The 
release pressure line, as shown at the right hand end 
of the diagram, should fall perpendicular when the 
piston begins to return. 

The capacity of the suction and discharge pas- 
sages can also readily be tested by decreasing the 
speed of the pump, and should the suction and 
discharge pressure materially decrease, the area in 
the passages is insufficient for such a speed and 
should be enlarged. 

DIAGRAM FROM BOILER FEED PUMP SHOWING LEAK- 
AGE IN THE DISCHARGE PASSAGES. 

Fig. 72 shows a diagram from the water cylinder of 
a pump 4"x2|"x4". Boiler pressure 37. The compres- 
sion curve as shown at the right hand end of the dia- 
gram leans inward, and shows that the pressure com- 
menced to release before it exceeded the boiler pres- 



Practical Application of the Indicator. 143 

sure, and indicates a leak in the plunger, suction 
valves on the suction side of the plunger, discharge 
pipe or heater. The discharge pressure proper is two 
pounds greater than the boiler pressure, and is a 
moderate loss. The release pressure curve, as shown 
at the left hand end of the diagram, leans inward 
and indicates that the pressure was partly maintained 
on the suction side of the plunger for a considerable 
distance, and indicates a leak in the discharge valves 
on this end of the cylinder, or in the plunger, or 
both. The supply pressure was 3 pounds, and the 





Fig. 72— Scale of Spring 30. 



distance between the atmospheric line and the suction 
line measures 2 pounds, and is also a moderate loss. 
The speed of the pump was then decreased, and 
the discharge pressure fell to 18 pounds or 19 pounds 
less than the boiler pressure, in which case no water 
could pass into the boiler but passed through the 
leaks, and a search for the leakage was made at every 
point between the boiler and the water cylinder, as 
follows: The pump was run at a moderate speed 
and a valve on the discharge pipe next to the boiler 
was closed, and the pump should have stopped had 
there been no leakage. But the speed decreased 



144 Practical Application of the Indicator. 

only slightly ; another valve between the heater and 
next to the pump was closed, and the speed decreased 
fifty per cent., thus showing that there was about an 
equal amount of leakage in the heater and in the 
pump. Had the pump then stopped, all the leakage 
would have been in the heater, or had the speed been 
maintained, the leakage would have been in the 
pump. 

Fig. 73 was taken from the same pump under a 
high speed, and it created a suction of g\ pounds. 



Fig. 73— Scale of Spring 30. 



When the plunger returns the compression curve erects 
at about one-half stroke, showing that the cylinder 
was only half full of water, and the speed was be- 
yond the capacity of the suction passages. Had 
there been no leakage out of the cylinder, this com- 
pression curve should have been erected perpendic- 
ular at the point where it rises above the atmospheric 
line instead of forming a curve neither a concave nor 
a convex. Frequently pumps are replaced with 
larger ones, and have failed to produce any better 
results, from the fact that the difficulty was due to 



Practical Application of the Indicator. 145 

insufficient area in the suction passages. The peak 
above the diagram at the commencement of the dis- 
charge line is caused by a shock from the rapid rising 
in pressure. 

DIAGRAM SHOWING ABSENCE OF ELASTIC CUSHION 
CAUSING IRREGULARITIES IN THE DISCHARGE LINE. 

Fig. 74 is taken from the water cylinder of a 
pump where all passages were practically free from 




Fig. 74— Scale of Spring 40. 



leakage, as is shown by the perpendicular com- 
pression and release pressure line. The air cushion 
chamber on the discharge was filled with water, and 
the absence of any elastic cushion, caused shocks 
and intermittent action in the discharge pressure, and 
formed the abrupt irregularities in the discharge pres- 
sure line. When the water was removed from the 
air chamber, the discharge line was straight. The 
absence of an air vent at the top of the air cushion 
chamber renders it practically impossible to drain the 



146 Practical Application of the Indicator. 

chamber of water, and when the chamber is filled it 
causes the pump to run noisy, about the same as 
when the cylinder is only partly filled with water. 

PECULIAR COMPRESSION AND RELEASE PRESSURE LINES. 

Fig. 75 shows a diagram from the steam cylinder 
of a 4"X3"X4" Duplex Boiler Feed Pump. The 
upper diagram was taken when the pump was running 
at a moderate speed, sufficient to supply the boiler. 
The release curve as shown at the right hand end of 
the diagram, curves inward and indicates that the ex- 
haust port was not sufficiently open to properly release 
the pressure before the piston commenced to return. 
The back pressure in the beginning of the back pres- 
sure line is 12 pounds and gradually falls to about 6. 5 
pounds at about three-quarter stroke, when it grad- 
ually rises until the exhaust valve closes. The ex- 
cessive back pressure is caused by insufficient area in 
the exhaust passages, either in the ports or in the ex- 
haust pipe, a matter which can readily be determined 
by placing a gauge on the exhaust pipe or by taking 
an exhaust pipe diagram with the indicator. Should 
the back pressure in the exhaust pipe be moderate, 
the restricted area would be in the ports, and should 
the back pressure in the pipe be the same as the indi- 
cated back pressure on the diagram, the restricted 
area would be in the exhaust pipe. 

Back pressure is a loss of power and economy be- 
cause it requires an additional amount of steam on 
the admission side of the piston to overcome it and 
should the back pressure equal the admission pressure, 
the pump would stop. 



Practical Application of the Indicator. 147 

The compression curve as shown at the left hand 
end of the diagram is formed by the live steam being 
admitted into the cylinder before the piston completes 
its stroke as the exhaust lap is only sufficient to pre- 
vent the entering steam from passing into the exhaust, 
which is the general method of cushioning a steam 
pump. 

The speed of the pump was then decreased and 
the pencil again applied when the admission pressure 
fell to only 5 pounds as shown in the diagram between 
the upper diagram and atmospheric line. The boiler 
pressure was 75 pounds which multiplied by the area 





-? 



Fig. 75— Scale of Spring 40. 

of the plunger 7.06 inches, gives a total of 529.5 
pounds resistance. And since the area of the steam 
piston is 12. 56 inches, multiplied by the admission pres- 
sure 5 pounds, gives 62. 8 pounds exerting pressure, thus 
showing. that it was impossible to force the water into 
the boiler. Upon searching, it was found that the 
water passed through leaks in the heater. This dia- 
gram is considerably shorter and is caused by the 
velocity of the parts being less and is stopped at 
an earlier point in the stroke and this reduction 
in the stroke increases the percentage of clearance 
an amount proportionate to the difference in the 
length of the two diagrams. 



148 



Practical Application of the Indicator. 



Owing to the short stroke of the pump, no reduc- 
ing motion was necessary in taking the diagrams. 

Fig. 76 shows a diagram taken from the water end 
of the same pump and will bear considerable study. 
The compression line is shown at the right hand end 
of the diagram as curving outward and shows that the 
pressure rises to about one-half the discharge pressure 
on the suction side of the plunger while the plunger 
is still moving away and is caused by leakage of water 




Scale of Spring 40. 



into the cylinder through the discharge valve on the 
suction side of the plunger. When the plunger com- 
mences to return the line is then completed by curving 
inward and is caused by leakage out of the cylinder 
through the suction valves on the discharge side of the 
plunger, or the plunger or both. The discharge line 
should be maintained horizontal to the end of the 
stroke but it will be seen that the pressure falls before 
the end of the stroke as shown by the release pressure 
line curving outward and is due to the fact, that be- 



Practical Application of the Indicator. 149 

fore the plunger stops, it is moving slowly and the 
pressure leaks out of the cylinder and the water es- 
capes through the leaks at a lower pressure than that 
required to force it into the boiler. When the return 
stroke commences, the completion of this line should 
fall perpendicular but instead, it completes by curving 
inward and is caused by leakage into the cylinder on 
this suction side of the plunger and the pressure is not 
fully released until the plunger has moved a short dis- 
tance on its return stroke. 

The water was supplied by pressure but the insuf- 
ficient area in the supply passages even caused it to 
fall below the atmospheric line and created a vacuum 
in the cylinder, and together with the speed not 
being uniform throughout the stroke it formed ir- 
regular suction line at different points in the stroke 
as shown. 

When the speed was reduced the pencil was again 
applied and the smaller diagram was obtained. The 
discharge pressure is only 14.5 pounds and the boiler 
pressure was 75 pounds, thus showing that the water 
could not pass into the boiler and the leakage was 
found to be in the heater. The decreased speed of 
the pump reduced the length of the stroke and formed 
the shorter diagram as shown. 



CHAPTER XL 

CALCULATING THE MEAN EFFECTIVE PRESSURE BY 
ORDINATES. 

The mean effective pressure (M. E. P.) is the 
average pressure per square inch on the piston during 
its entire stroke, less the back pressure on its return 
stroke. 

To calculate the M. E.P. by the ordinate process, 
the height in pounds of each ordinate is measured on 
the scale of the spring from the back pressure line 
and compression curve to the steam line and expan- 
sion curve, whether condensing or noncondensing. 
The ordinates must be equal distances apart and per- 
pendicular to the atmospheric line. The first ordinate 
is located at the point of exhaust closure as shown in 
Fig. 77, and no other ordinate between it and the 
admission line is necessary, except in diagrams taken 
from high speed engines where the exhaust valve 
closes at an early point in the stroke. This ordinate 
measures 72 pounds, and is the pressure exerted on 
the piston during this part of the stroke, providing 
there was no compression, and that the steam line was 
parallel to the atmospheric line. But a deduction 
must be made for the compression, and to do this, 
another measurement is made at such a point between 
this ordinate and the admission line, as to represent 
the average pressure during this range of the piston 
movement, and in this case is located at such a point 

150 



Practical Application of the Indicator, 



151 



as shown by the dotted ordinate which measures 70 
pounds ; therefore, the first ordinate proper should 
read yo pounds instead of 72 pounds. The remain- 
ing portion of the diagram is divided with ordinates 
whose distances apart are the same as the distance 
between the admission line and the first ordinate 
proper and measures respectively, 72, 41, 30, 23, 18, 
1 3j 9- 5j 6.5, 4 pounds. The greater the number of 
ordinates employed, the nearer correct will be the 




Fig. 77— Scale of Spring. 40. 



calculation ; however, about ten (the same as em- 
ployed in this diagram) will be sufficient. Their total 
sum is 287 pounds. The total sum of the ordinates 
on the diagram from the other end of the cylinder is 
determined in like manner. Supposing this is 288 
pounds. The two sums combined and divided by 20, 
which is the number of ordinates contained in both, 
diagrams, gives the M. E. P. Then 2874-288^-20 = 
28.75 pounds M. E. P. and is the factor used in com- 
puting the indicated horse power (I. H. P.) Had the 



152 Practical Application of the Indicator. 

number of ordinates been 30, the sum of the two 
totals should have been divided by 30, and so on. 

It is of importance that the ordinates be equal 
distances apart, and unless they extend to the end of 
the diagram, as shown by the arrow, which is the 
tenth ordinate, the fraction must be known. This 
however, can readily be computed on the scale of any 
spring. The distance between the ordinates proper, 
measures 14 pounds on a 40 scale; and supposing the 
distance between the ninth ordinate and the end of 
the diagram measures 6 pounds, the fraction is iV-hs, 
and is reduced to decimal by dividing 6 by 14. Thus 
6-4-14=. 42 ; therefore, the number of ordinates in 
the diagram is 9.42 ; and supposing the ordinates on 
the diagram from the other end of the cylinder also, 
is 9.42. Then 9.42+9.42=18.84, and is the number 
of ordinates contained in both diagrams. Supposing 
the average height in pounds of the ordinates con- 
tained in both diagrams is 575. Then 575^-18.84 = 
30.52 pounds M. E. P. Should the expansion curve 
merge into the back pressure line before the end of 
the diagram, and follow the back pressure line to its 
end, nevertheless the total sum in pounds of the ordi- 
nates must be divided by the number of the ordinates 
which must extend to the entire end of the diagram, 
or the same as if the expansion curve was maintained 
above the back pressure line. 

Where the load is constantly changing, the pencil 
should be applied during as many revolutions as is 
necessary, in order to obtain both the lightest and 
heaviest load, as shown in Fig. 78, from which the M. 
E. P. can be calculated, and the ordinates are located 



Pi-actical Application of the Indicator. 



153 



in the usual manner. The first ordinate proper, when 
corrected for the compression curve measures 68 
pounds, and the second ordinate has two measure- 
ments, viz : the earliest and the latest points of cut- 
off. The first measures 56 pounds and the second 73 
pounds. The remaining ordinates are measured in 
like manner, which are respectively, 35-44, 24-31, 
16.5-22, 11-16, 7-1 1, 4-8, 2-5.5, J -4> giving a total 
sum of 439 pounds. The sum of the ordinates on 




Fig. 78— Scale of Spring 40. 



the diagram from the other end of the cylinder is 
calculated in like manner. Supposing this is 221 
pounds; then 439+22 i-f- 38- 17. 36 pounds M. E. P. 
It will be seen that the total sum of the ordinates 
from the two diagrams must be divided by the num- 
ber of measurements contained in both diagrams, 
which is 38, as 18 of them have two measurements. 
The average height of the nine ordinates may also 
be found by making single measurements half-way 
between the lowest and highest expansion curves. 



154 



Practical Application of the Indicator. 



When a loop is formed in the diagram as shown 
in Fig. 79, the total sum of the ordinates contained 
in the loop of the diagram from each end of the cyl- 
inder must be deducted from the total sum of the- 
ordinates contained in the exerting portion of the 
diagrams and the result divided by 20, which is the 
number of ordinates contained in both diagrams, and 
this gives the M. E. P. The ordinates in the loop of 
this diagram measures respectively, 3, 5, 7, 4 pounds, 




or a total of 19 pounds ; and supposing the total sum 
of the ordinates in the loop on the diagram from the 
other end of the cylinder measures 1 1 pounds. Then 
19+11 = 30 pounds. The height of the ordinates in 
the exerting portion of this diagram measures respect- 
ively 69, 30, 16.5, 9, 3.5 pounds, or a total of 128 
pounds. And supposing the total sum of the ordi- 
nates in the exerting portion of the diagram from the 
other end of the cylinder is 122 pounds, plus I28„ 
gives 250 pounds; then 250—30-^20=11 pounds M. 



Practical Application of the Indicator. 155 

E. P. The expansion curve crosses the back pressure 
line at the sixth ordinate, and there is no pressure 
above or below the back pressure line at this point, 
but nevertheless this point counts as an ordinate, 

The M. E. P. can also be readily determined by 
making a continuous measurement on a strip of paper 
near its edge (which must be straight), and carried 
from one ordinate to another, the measurement of 
each being marked beyond the preceding one, so that 
the distance from the end of the strip to the last 
mark, represents the height of the ordinates com- 
bined. The distance as shown in Fig. J7, is 7.01 
inches ; and supposing the distance on the diagram 
from the other end of the cylinder is 7.25 inches, then 
7.01+7.25 = 14.26, and since the scale of the spring 

is 40; then 14.26x40 , ' _ ^ 

— —=28.52 pounds M. E. P. 



CHAPTER XII. 

THE PLANIMETER. 

The planimeter is an instrument for measuring the 
square inches of area of an indicator diagram, or any 
figure that has a plain surface. This instrument has 
become almost indespensible to the engineer, and is 
the only accurate method of determining the M. E. 
P. of an indicator diagram. Its operation is very 
simple, and it can be readily manipulated by any 
person of ordinary intelligence. Fig. 80 shows the 
planimeter properly applied to an indicator diagram. 

To calculate the M. E. P. with the planimeter : 
First, the diagram is made fast on the drawing- 
board by a thumb tack at each end, and placed as 
shown in Fig. 80. The surface on which the roller 
is traveling must be perfectly smooth and unglazed. 
A piece of dull cardboard serves the purpose satis- 
factorily, and should be placed underneath the dia- 
gram and extend sufficiently above it to give ample 
traveling surface for the roller. The tracing point 
should be pressed sufficiently into the paper so as to 
form an impression as a starting^a-nd stopping point. 
This point must be on the back pressure line, and at 
about the middle of the diagram. The stationary 
point as shown at the left is pressed fast into the 
board, on about an equal plane with the back pres- 
sure line and about the same distance from the trac- 
ing point as the length of the diagram. If the card 

156 



Practical Applicatio?i of the Indicator. 



157 



on which the diagram is taken, contains spaces above 
the diagram for recording various observations, and 
they extend such a distance above the diagram as to 
interfere with the roller, the diagram should be placed 
upside down. 

With the planimeter in proper position as shown, 




Fig. 80. 

adjust the roller so that its zero coincides with the 
zero of the vernier, as shown in Fig. 80. Then cir- 
cumscribe the diagram in the direction indicated by 
the arrow, or that of the hands of a watch, and with 
such precision that the tracing point follows the pre- 
cise path of the pencil until it returns to the starting 



158 



Practical Application of the Indicator. 



point. Supposing the reading to be the same as 
shown in Fig. 81. The roller is divided into ten num- 
bered parts, and each number represents one square 
inch. Had figure 2 on the roller exactly coincided 
with the zero on the vernier, t«he result would have 
been 2 square inches without any fraction. The spaces 
between the numbers are divided into ten graduations, 
each of which represents 1-10 of a square inch; and 
had the first graduation coincided with the zero on 







> i 


i ' 


°r 




111 

l',J 


2 


ill 


111 

3 


III} 


niji; 















Fig. 81. 

the vernier, the result would have been 2.1. The 
vernier also has ten graduations, and if one of them 
coincides with a graduation on the roller, it represents 
— counted from zero — so many hundredths of a square 
inch. In this case, the fourth graduation of the ver- 
nier coincides with one of the graduations of the 
roller, and the final reading is 2.14 square inches.. 

Referring again to the reading as indicated by the 
planimeter, it is plain to be seen that Fig. 2 on the 
roller, has passed the zero on the vernier, therefore, 



Practical Application of the Indicator. 159 

figure 2 may be first marked down. It also shows 
that there is one graduation between the figure 2 on 
the roller and zero on the vernier, and therefore fig- 
ure i is next marked down, and a decimal point must 
be placed between it and figure 2. It also shows that 
the fourth graduation on the vernier coincides with 
one of the graduations on the roller and is the last 
figure marked down, and the reading is as before 
stated, 2.14 square inches. It can readily be seen 
from the above explanation that the method of read- 
ing the planimeter is a simple undertaking. Suppos- 
ing the scale of the spring is 40, and the length of the 
diagram (which is measured on the atmospheric line) 
is 4 inches, and the area of the diagram from the 
other end of the cylinder is 2.26 inches; the M. E. 
P. is then found by multiplying the combined area in 
square inches contained in the diagram from each end 
of the cylinder (4.40) by the scale of the spring (40) 
which gives 176.00, and instead of dividing 176.00 
first by 4, that being the length of the diagram in 
inches, and the quotient by 2, so as to obtain the 
average pressure on the piston from both ends of the 
cylinder; it is necessary only to divide 176.00 by two 
times four: 

Example, 2. 26+2. 14x40 1 at t- -n 

v > 1 <+ — ^__ 22 p 0unc j S) m. E. P. 

To determine the length of the diagram, a scale 
graduated in one-hundredths of an inch should be 
used, otherwise it frequently requires figuring on the 
scale of any other spring to learn its length. Sup- 
posing the length of the diagram is 3 inches and 30 
pounds on a 40 scale. The pounds is reduced to 



160 Practical Application of the Indicator. 

inches by dividing it by the scale of the spring: Ex- 
ample, 30-7-40=. 75 of an inch, and the length of the 
diagram is then 3.75 inches. Supposing the combined 
area of the diagram from each end of the cylinder is 4 
inches, multiplied by 40 gives 160 without any frac- 
tion, and since there is a fraction of two figures to 
the right of the decimal in the divisor (3.75), there- 
fore, two ciphers should be added to the dividend, 
when it will read 160.00, and so on, or in other words, 
unless the fraction either in the divisor or dividend 
contain the same number of figures to the right of 
the decimal, ciphers should be added accordingly, the 
example then becomes: 

4 x 40 =2 1. 33 pounds, M. E. P. 

3.75X2 " F 

The planimeter is a delicate instrument and should 
be carefully handled. The roller should be taken out 
and the bearings cleaned and oiled with porpoise 
jaw oil, the same as used on the pencil motion 
of -the indicator. After replacing the roller, the 
roller-shaft should be adjusted so that there is no 
end play and that the roller revolves with perfect 
freedom, a matter which should be occasionally 
tested before using the planimeter. 

Where a diagram is taken from each end of the 
cylinder on the same card, as shown in Fig. 82. It 
is unnecessary to make two separate readings. After 
circumscribing the diagram from one end of the cylin- 
der, continue to circumscribe the diagram from the 
other end of the cylinder in the direction as indicated 
by the arrows, and when the tracing point has again 
reached the starting point, the result is a double read- 



Practical Application of the Indicator. 161 

ing, which in this case is 5.38 square inches. The 
length of the diagram is 3.51 inches, then 

5.38X40 ^ 65 pounds? M E P 

3.51X 2 

Where the load is constantly changing as shown 
in Fig. 78, the diagram must be circumscribed twice. 
Commencing with the tracing point in the usual place 
and circumscribe the diagrams at the earliest and 
latest -points of cut-off, thus giving a double reading. 




Fig. 82— Scale of Spbing 4<J. 

Supposing this is 4.84 square inches, and another 

double reading of the diagram from the other end of 

the cylinder is 4.78 square inches: Scale of the 

spring is 40 and the length of the diagram 3. 5 inches, 

then 4.84+4.78x40 „ j at t- -n 

Z — z ' ^ ' z_=27.48 pounds, M. E. P. 

3.5X4 
The reason for multiplying 3.5 by 4 is, that there 
are two double readings, and the easiest cut-off 
represents the lightest load and the latest cut-off 
the heaviest load. 



162 



Practical Application of the Indicator. 



When diagrams contain loops as shown in Fig. 83, 
the loops must be circumscribed in the opposite direc- 
tion, as indicated by the arrows, and in this way the 
planimeter automatically deducts the area contained 
in the loops from the exerting portion of the diagrams. 




Fig. 83. 



The area of the diagram from the other end of the 
cylinder is determined in like manner and their 
lengths are measured on the atmospheric line, and 
the process of calculating the M. E. P. is made in 
the usual manner. 



CHAPTER XII. 

TO COMPUTE THE INDICATED HORSE - POWER OF AN 
ENGINE. 

The commonly accepted valuation of a horse- 
power is 33,000 pounds raised one foot high in one 
minute, or its equivalent. 

The rule for finding the horse-power of an engine 
is: Multiply the area of the piston, less one-half the 
area of the piston-rod, by the mean effective pressure 
and this by the speed of the piston in feet per minute. 
This product divided by 33,000 will give the indicated 
horse-power (I. H. P.) of the engine. 

Supposing it be desired to compute the I. H. P. 
of an engine having the following data: Diameter of 
piston, 20". Diameter of piston rod, 3". Stroke,. 
42". Revolutions, 70. M. E. P., 30.5 pounds. 

The area of the piston is found by multiplying the 
-square of its diameter by .7854. 

Example, 20" X20" X. 7854=314. 16". 

One-half the area of the piston-rod is found by 
multiplying the square of its diameter by .7854 and 
dividing by 2. Example, 3" X 3" X .7854-^-2 = 3. 53". 
Then 314. 16" — 3. 53" = 3io.63" net area of piston. 
There being a piston-rod on but one side of the piston 
makes it necessary to deduct only one-half the area 
of the piston-rod. 

The speed of the piston in feet per minute is found 
by multiplying twice the stroke in inches and this 

163 



164 Practical Application of the Indicator 

divided by 12" (there being 12 inches to the foot) 
gives the feet per revolution, and this multiplied by 
the number of revolutions gives the feet per minute. 
Example, 42" x 2-r- 12" x 70=490 feet. The I. H. P. 
is then found in the following manner: 

3io.63' X3Q.5X490' = I4 o. 67LIL P . 

33000 

The horse power constant is the number of I. H. 
P. for each pound of M. E. P., and when the piston 
speed in feet per minute remains constant, this is the 
most rapid process of computing the I. H. P. as when 
the horse-power constant is once found it is only nec- 
essary to ascertain the M. E. P. and this multiplied 
by the horse-power constant gives the I. H. P., viz., 
net area piston 310.63". Piston speed in feet per 
minute 490. Then 3 10.63" X490' _. 6l2 H p q 

33000 

To ascertain the I. H. P. where the load is con- 
stantly changing, diagrams should be taken at about 
ten minute intervals for a duration of one or more 
hours according to the importance of the test, etc., 
and the pencil should be applied as many revolutions 
as necessary in order to obtain the lightest and 
heaviest load. 

The length of the diagrams is found by measuring 
the length of one of them. But should their length 
vary, in which case they are distorted and in order 
to obtain the average length, their combined length 
divided by the number of diagrams gives the average 
length, and supposing this is 4.25". Supposing the 
scale of the spring is 40, and the number of diagrams 
is 24, and that the point of cut-off varies so that each 



Practical Application of the Indicator. 165 

diagram has a double reading which is equal to 48 
diagrams, and their combined area which supposing 
is 96.45 multiplied by the scale of the spring and the 
product divided by 48 times the average length of the 
diagrams, gives the M. E. P. 

Example, 96.45x40 ^,3^ ds M R R 

48x4-25 

The I. H. P. for the entire duration of the test is 
then found in the usual manner. 

To ascertain the I. H. P. of one or more ma- 
chines it is only necessary to take a pair of diagrams 
with the machine in operation, and supposing the 
area of the diagrams is 4.38". Another pair of dia- 
grams is taken while the machine is not in operation, 
whose area is 3.14". Then 4. 38" — 3. 14" = 1.24" net 
area and is the factor used in computing the I. H. P. 
of the machine. 

To determine whether'the load is equally distrib- 
uted on each side of the piston, it is only necessary 
to find the area of the diagram from each side. 

To compute the I. H. P. from one end of the cylin- 
der the M. E. P. of the diagram from the head end of 
the cylinder multiplied by the area of the piston, in 
which case no deduction is made from the head end when 
there is no piston rod. (But the whole area is de- 
ducted from the crank end in computing the I. H. P. 
from the crank end.) This multiplied by one-half the 
piston speed in feet per minute, and divided by 33,000 
gives the I. H. P. from one end of the cylinder. 

To compute the I. H. P. of a two cylinder com- 
pound engine the M. E. P. of the high pressure 
cylinder divided by the ratio of the piston areas plus 



16(5 Practical Application of the Indicator. 

the M. E. P. of the low pressure cylinder multiplied 
by the horse power constant of the low pressure cyl- 
inder gives the I. H. P. of the engine. The ratio of 
the cylinder areas is found by dividing the net area of 
the low pressure piston by the net area of the high 
pressure piston, in which case when the cylinders are 
placed tandem the low pressure piston has two piston 
rods, and their areas combined and divided by 2 gives 
the average area which must be deducted from the low 
pressure piston. The net area of the high pressure 
piston is found in the same manner as in a single cyl- 
inder engine and the horse power constant of the low 
pressure piston is also found in the usual manner. 
Supposing it be desired to find the I. H. P. of an 
engine having the following data: Net area high pres- 
sure cylinder ioo". Net area low pressure cylinder 
300". Then 300" -moo" = 3. Ratio: M. E. P. high 
pressure cylinder 40; M. E. P. low pressure cylin- 
der 13; piston speed in feet per minute 500; horse 
power constant low pressure cylinder 5. 

Example, 40-=~3 + i3X 5 = 131.66 I. H. P. 

The I. H. P. may also be determined by com- 
puting the I. H. P. of each cylinder separately, the 
same as in a single cylinder engine, and their I. H. P. 
combined gives the I. H. P. of the engine. 

To ascertain the distribution of power as between 
the two cylinders instead of computing the I. H. P. 
of each cylinder it is only necessary to divide the 
M. E. P. of the high pressure cylinder by the ratio 
and should the quotient be the same as the M. E. P. 
in the low pressure cylinder the load is equally dis- 
tributed. 



CHAPTER XIII. 

TESTING THE PISTON AND VALVES FOR LEAKS. 

The piston and valves of an engine are never abso- 
lutely tight. To test the steam valves of a Corliss 
engine, unhook both steam valves and with the dash- 
pots properly seated so that the valves cover the ports 
in the usual manner, and with the tapped holes for 
the indicator open, admit the full pressure into the 
steam chest, and if steam escapes through the tapped 
holes the steam-valves leak. 

To test the piston and exhaust valves, place the 
engine on the center, supposing the head end, discon- 
nect the crank end exhaust valve and place the valve 
so as to properly cover the port. Place the wrist- 
plate toward the crank end and with the head end 
steam valve hooked in admit the full pressure into the 
head end clearance space. If steam escapes through 
the exhaust pipe, the exhaust valve leaks, and if a 
greater quantity of steam escapes through the crank 
end tapped hole than the leakage of the crank end 
steam-valve, the piston leaks. The other exhaust 
valve is tested in like manner. 

To test the valve of a single valve engine, revolve 
the engine and with a tram at each position make a 
mark on the valve-stem; then equally divide the dis- 
tance and place the engine so that the tram spans 
the middle mark ; when ' the valve equally covers 
the ports admit the full pressure into the steam- 

167 



168 Practical Application of the Indicator. 

chest, and if steam escapes through the tapped holes 
the valve leaks. 

To test the piston, place the engine on the center 
and if the valve has lead admit the full pressure into 
the clearance space, and if a greater quantity of steam 
escapes through the tapped hole on the other side of 
the piston than the leakage of the valve, the piston 
leaks. 

This is the only positive test for determining the 
leakage of the piston and valves. 

TO ASCERTAIN THE PERCENTAGE OF CLEARANCE IN 
4N ENGINE. 

The clearance is the space embraced in the ports 
and between the piston and cylinder head when the 
engine is on the center. The piston and valves must 
be made absolutely tight, otherwise the result is mis- 
leading. 

First, place the engine one inch travel on the cross- 
head, remove the cylinder-head, then pack the piston 
tight with asbestos, or other suitable substance. After 
replacing the cylinder-head make the valves tight by 
placing the sheet packing between the valve and seats, 
in which case the valve must be held tight to the seats; 
but, if a piston valve, remove it and place sheet pack- 
ing over the port, which can be held in place by a 
segment made of wood, whose radius is less than the 
thickness of the packing. If the cylinder is tapped 
on the side for the indicator, extend the filling pipe 
above the cylinder and fill this space with water. 
Supposing its weight is 55 pounds, then place the en- 
gine on the center; and supposing that 30 pounds of 



Practical Application of the Indicator. 169 

this water is discharged, then 30 pounds is the weight 
of the water contained in the cylinder for each inch 
of the piston movement. Supposing that the weight 
of the water in the filling pipe is one pound, then the 
remaining 24 pounds is the weight contained in the 
clearance space. Supposing the stroke of the engine 
is 40", then 

— —.02 (2 per cent.) clearance 

30x40 

It will be seen from the above explanation that 

this is a remarkably simple, quick and accurate method 

of ascertaining the percentage of clearance, and that 

the displacement of the piston-rod is automatically 

deducted from the crank end of the cylinder. 

METHOD OF LOCATING THE CLEARANCE LINE AND DE- 
TERMINING LEAKAGE ON THE DIAGRAM. 

The clearance contained in the head end of the 
cylinder must be added to the head end diagram, and 
the clearance of the crank end to the crank end dia- 
gram. In Fig. 84 the clearance line is shown at the 
left of the diagram. Supposing the percentage of 
clearance is .025 (2 \ per cent.) the length of the dia- 
gram 4", then .025x4" = . 1 ", and is the distance the 
clearance line should be located from the commence- 
ment of the atmospheric line and at right angles. 
This can be reduced to pounds by multiplying it by 
the scale of any spring, thus, 40 X- 1"=4 pounds, and 
this distance must be located with the same scale, 
and so on. 

To determine from the diagram the leakage of the 
^valves and piston seems to be a popular craze with 



170 



Practical Application of the Indicator. 



some engineers. While demonstrations are mathe- 
matically correct, yet there are other factors to be 
considered which are not shown in the diagram, and 
to base any facts upon a false expansion curve is a 
misleading and costly undertaking. Chief among 
these factors are an incorrect indicator, leakage of 
the piston and exhaust valve, which may be balanced 
with re-evaporation ; leakage of the steam-valve, 




Fig. 84 — Scale of Spring 40. 

which may be balanced with condensation, and the 
leakage into and out of the cylinder may balance 
each other, when the engine will produce an expan- 
sion curve representing a perfect expansion of steam. 
The demonstration as shown in Fig. 84 is remark- 
ably simple, and can be readily applied to any dia- 
gram. Locate the vacuum line on the scale of the 
spring at such a distance below the atmospheric line 
as to represent the atmospheric pressure at the time. 



Practical Application of the Indicator. 171 

and place; also the clearance line representing the 
percentage of clearance on this end of the cylinder. 
Should the clearance not be known, and for such a 
purpose an approximation may be made, as a reason 
able variation in the location in the clearance line 
varies but slightly in the expansion curve. Then 
locate a perpendicular ordinate from a point in the 
expansion curve, as shown by the first dotted ordinate, 
in which case the steam valve has fully closed, as 
shown by the expansion curve in changing from a con- 
vex to a concave curve, and the pressure at this point 
is 80 pounds absolute. Then locate another ordinate 
at a point double this distance from the clearance line, 
as shown by the second dotted ordinate, in which case 
the volume is doubled, and the pressure should be 
one-half of that at the first dotted ordinate, or 40 
pounds absolute, providing that steam was a perfect 
gas. If the pressure is greater than 40 pounds the 
steam -valve has leaked and raised the expansion 
curve, and if less, the piston or exhaust-valve, or 
both, have leaked and lowered it. 



CHAPTER XIV. 

LOCATING THE THEORETICAL CURVE. 

The theoretical curve represents a figure in which 
the volume is inversely as the pressure. Thus, if one 
cubic foot of perfect gas at ioo pounds absolute pres- 
sure be expanded into two cubic feet, the volume is 



Fig. 85. 

doubled, and the pressure is one-half or 50 pounds 
absolute, and so on. When this curve is applied to 
an indicator diagram it is of no -more value than Fig. 
84; except that it shows the corresponding pressure 
at any point in the expansion curve. Fig. 85 shows 
the method of applying it to an indicator diagram. 
With the clearance and vacuum lines added, locate 

172 



Practical Application of the Indicator. 173 

the perpendicular line at a point beyond the cut-off, 
as explained in Fig. 84; and from this point where it 
intersects with the expansion curve, locate the upper 
line at right angles, as shown. Then from this line 
locate the ordinates perpendicular, and about the 
distance apart, as shown and from each of these 
intersections, locate the diagonal lines to the inter- 
section of the clearance and vacuum lines. Then 
from the point where the first diagonal line crosses 
the cut-off line, draw the dotted horizontal line inter- 
secting with the first ordinate at a point shown by the 
dotted curve, and so on. If the expansion curve of 
the indicator diagram rises above the theoretical 
curve it indicates leakage of steam into the cylinder, 
and should it fall below the theoretical curve, it indi- 
cates leakage out of the cylinder. 

LOCATING THE THEORETICAL POINT OF CUT-OFF. 

To locate the theoretical point of cut-off, as shown 
in Fig. 86; the clearance and vacuum lines must be 
added in the usual manner. The initial pressure line 
as shown above the diagram, should be located such 
a distance above the steam line as to allow for the 
friction of the indicator, because owing to the fric- 
tion, the indicator gives less pressure while rising, 
and more while falling. 

Supposing it be desired to determine the theoreti- 
cal point of cut-off for the purpose of ascertaining the 
I. H. P. for a given point of cut-off, in which case 
all the leakage into and out of the cylinder must be 
calculated from a point just before the exhaust valve 
opens, which gives the point of cut-off corresponding 



174 



Practical Application of the Indicator. 



to this pressure. Therefore, the base line is located 
perpendicular at a point as shown, then locate the 
diagonal line between the two intersections as shown, 
and next the horizontal line at right angles from the 
intersection of the base line and the expansion curve, 
which represents the distance of the theoretical point 
of cut-off, and this distance is transferred on the initial 
pressure line. From this point the cut-off line is located 




Fig. 86. 

perpendicular, and represents the theoretical point of 
cut-off corresponding to the pressure of the base line. 

COMPUTING THE WATER CONSUMPTION PER INDICATED 
HORSE POWER PER HOUR FROM THE DIAGRAMS. 

To compute the water consumption of an engine 
from the diagram is a worthless and misleading 
method, from the fact that condensation can not be 
accounted for, and the leakage into and out of the 



Practical Application of the Indicator 175 

cylinder, may balance each other, etc. Supposing it 
be desired to compute the water consumption of Fig. 
87, having the following data: Diameter cylinder 
20", stroke, 42", diameter piston-rod, 3", length pis- 
ton-rod, 42.5", revolution, 70, clearance head end, 
3 per cent., clearance crank end, 2 per cent. 

One-half the piston-rod displacement in cubic 
inches, is found by multiplying the square of its diam- 



Fig. 8' 



eter'by .7854 by its length and divided by 2 : Thus, 
3" X 3"X. 7854x42. 5 ff -f-2=i50.20 cubic inches. The 
mean piston displacement per stroke in cubic feet is 
found by multiplying the square of the diameter of the 
cylinder in inches by .7854 by the stroke, less one-half 
the piston-rod displacement, and the product divided 
by 1728, that being the cubic inches in a cubic foot. 
Thus: 20" X20" X. 7854x42" — 1 50. 20 -f- 1728 =1 7.548 
cubic feet of mean piston displacement per stroke. 



176 Practical Application of the Indicator. 

The mean clearance is two and one-half per cent.. 
(.025) and the length of the diagram is 3.5". Then 
•O25X 3. 5 " = .08", and is the distance the clearance 
line should be located from the commencement of 
the diagram, the vacuum line being located the usual 
distance. Next locate a line from the clearance line 
parallel with the atmospheric line intersecting with 
the expansion curve, at a point just before the exhaust 
valve commences to open (as shown by the dotted 
line), so that all the transactions taking place in the 
expansion curve may be accounted for in the compu- 
tation. The length of the dotted line is 3.40"; and 
supposing the length of this line on the diagram from 
the other end of the cylinder is 3.20", then the mean 
is 3.30". The length of the diagram plus the clear- 
ance, is 3.58". The absolute pressure at the location 
of the dotted line is 23 pounds, and supposing the 
absolute pressure of the diagram from the other end 
of the cylinder is 27 pounds, then the mean absolute 
pressure is 2.5 pounds, and weighs according to the 
tables on properties of saturated steam .0634 pounds 
per cubic foot, and since the piston displacement per 
stroke in cubic feet is 7. 548, then 3. 30" x 7. 548 x .0634 
-4-3. 58 " = .441 1 pounds per stroke, providing there was 
no compression. But a deduction for the compressed 
exhaust steam must be made, and since the mean 
piston displacement in cubic feet is 7. 548, and the 
mean clearance is two and one-half per cent., then 
7. 548 X. 025 = . 1887 cubic feet of mean clearance per 
stroke. The compression is 45 pounds absolute ; and 
supposing the compression of the diagram from the 
other end of the cylinder is 35 pounds, the mean is 



Practical Application of the Indicator. 177 

40 pounds, whose weight per cubic foot is .0994; 
then . 1887X. 0994=. 0187 pounds per stroke. 

Since the revolutions per minute is 70 or 140 
strokes, the strokes per hour is 8400 ; and supposing 
the I. H. P. is 140, then .4411 — .0187x8400-^140= 
25.34 pounds water consumption per I. H. P. per 
hour. 



CHAPTER XV. 

Table No. i. 
temperature of vacuum. 



Pounds per 
square in. 


Temperature. $*"£ 


Pounds per 
square in. 


Temperature 


Inches of 
Mercury. 


I. 127 


208 


2.3028 


I3.I82 


116 


26.8608 


2.186 


204 


4.4538 


13 


345 


1 12 


27. I908 


3-172 


200 


6.4638 


13 


493 


108 


27.4908 


4.095 


I96 


8.3428 


13 


624 


104 


27.7588 


4-954 


192 


IO.O948 


13 


743 


100 


28.OO38 


5-755 


188 


II.7258 


13 


852 


96 


28.2238 


6.497 


184 


'13.2418 


13 


948 


92 


28.4218 


7.190 


l80 


I4.6508 


14 


035 


88 


28.5988 


7-333 


I76 


15.9588 


14 


114 


84 


28.7588 


8.427 


172 


17. 1718 


14 


183 


80 


28.8988 


8.978 


168 


18.2948 


14 


245 


7 6 


29.O249 


9.489 


164 


I9-3338 


14 


300 


72 


29.1374 


9-959 


l6o 


20.2928 


14 


350 


68 


29.2372 


10.393 


156 


2 1. 1768 


14 


393 


64 


29.3256 


10.792 


152 


21.9928 


14 


43i 


60 


29.4O38 


1 1. 162 


I48 


22.7428 


14 


465 


56 


29.4726 


11.499 


144 


23-43I8 


14 


495 


52 


29-5335 


11. 811 


I4O 


24.0638 


14 


521 


48 


29. 5867 


12.093 


136 


24.6418 


14 


543 


44 


29^334 


12.352 


132 


25. I718 


14 


563 


40 


29.6742 


12.591 


128 


25.6548 


14 


581 


36 


29.7097 


12.807 


124 


26.O958 


14 


596 


32 


29.7407 


13.004 


120 


26.4968 









178 



Practical Application of the Indicator. 



179 



Table 2. 
properties of saturated steam. 



Absolute 


Temperature 

in Fahrenheit 

degrees. 


Total heat- 


Heat-units 


Weight in 




pressure in 


units per 


per pound 


decimals of a 


Specific 


pounds per 


pound above 


contained in 


pound per 


volume. 


square inch. 


zero (32 ). 


the water. 


cubic foot. 




I 


I02 


1145 


I02. I 


.OO3O 


20620 


2 


126.3 


115,2.5 


126.4 


.OO58 


10720 


3 


141. 6 


1157 


I 


I4I-9 


.OO85 


7326 


4 


I53.I 


I I 6O 


6 


153-4 


.OI 12 


56OO 


5 


162.3 


H63 


4 


l62.7 


•0137 


4535 


6 


170. 1 


II65 


8 


I70.6 


.Ol63 


3814 


7 


176.9 


II67 


9 


177-4 


.OI89 


3300 


8 


182.9 


I 169 


7 


183.5 


.0214 


2910 


9 


188.3 


II7I 


4 


188.9 


0239 


2607 


10 


193.2 


I 172 


9 


193-9 


.O264 


2360 


1 1 


197.8 


1174 


2 


198.5 


.0289 


2157 


12 


202 


1175 


5 


202.7 


.0313 


1988 


13 


205.9 


1176 


•7 


206.7 


.0337 


1846 


14 


209.6 


1177 


9 


210.4 


.O362 


1722 


M-7 


212 


1178 


6 


212.9 


.O38O 


1644 


15 


213-1 


1178 


9 


213.9 


.O387 


1612 


16 


216.3 


I 179 


9 


217.2 


.0413 


1514 


17 


219.4 


Il80 


9 


220.4 


•0437 


1427 


18 


222.4 


Il8l 


8 


223.4- 


.O462 


I35i 


19 


225.2 


Il82 


6 


226.3 


.O487 


1282. 1 


20 


227.9 


II83 


■5 


229 


.05II 


1220.3 


21 


230.5 


II84 


2 


231-7 


.0536 


1 164.4 


22 


233 


1185 




234.2 


.O561 


IH3-5 


23 


235-4 


II85 


7 


236.7 


.0585 


1066.9 


24 


237.7 


II86 


5 


239 


,06lO 


1024. 1 


25 


240 


II87 


1 


241-3 


.0634 


984.8 



180 Practical Application of the Indicator. 

Table 2 — Continued. 



Absolute 
pressure in 


Temperature 
in Fahrenheit 


Total heat- 
units per 


Heat-units 
per pound 


Weight in 
decimals of a 


Specific 


pounds per 


degrees. 


pound above 


contained in 


pound per 


volume. 


square inch. 


zero (32 ). 


the water. 


cubic foot. 




26 


242.2 


II87.8 


243-5 


.0658 


948.4 


27 


244-3 


I I88.5 


245-7 


.0683 


914 


6 


28 


246.3 


II89 


247.7 


.0707 


883 


2 


29 


248.3 


I I89/7 


249.8 


-073I 


854 




30 


250.2 


1 190. 3 


251.7 


•0755 


826 


8 


31 


252. 1 


1190.8 


253.6 


.0779 


801 


2 


32 


254 


1191.4 


255-5 


.0803 


777 


2 


33 


255-7 


1191.9 


257.3 


.O827 


754 


7 


34 


257-5 


1192.5 


259.1 


.O85I 


733 


5 


35 


259.2 


1 193 


260.8 


.O875 


7i3 


4 


36 


260.9 


H93-5 


262. 5 


.O899 


694 


5 


37 


262. 5 


1 194 


264.2 


.0922 


676 


6 


38 


264 


1 194. 5 


265.8 


.O946 


659 


7 


39 


265.6 


1195 


267.4 


.O97O 


643 


6 


40 


267. 1 


1195.4 


268.9 


.0994 


628 


.2 


4i 


268.6 


1195.9 


270.5 


. IOI7 


613 


4 


42 


270. 1 


1 196. 3 


272 


.IO4I 


599 


3 


43 


271.5 


1 196. 7 


273-4 


. IO64 


586 


1 


44 


272.9 


1197.2 


274.9 


.IO88 


573 


7 


45 


2 74-3 


1197.6 


276.3 


.1111 


561 


8 


46 


275.7 


1 198 


277.7 


•1134 


55o 


4 


47 


279 


1198.4 


279 


.1158 


539 


5 


48. 


278.3 


1198.8 


280.4 


•Il8l 


529 




49 


279.6 


1 199. 2 


281.7 


. I204 


518 


6 


50 


280.9 


1 199.6 


283 


. 1227 


508 


'5 


5i 


. 282.1 


1200 


284.2 


• 1251 


499 


1 


52 


283.3 


1200.4 


285.5 


.1274 


490 


1 


53 


284.5 


1200.7 


286.7 


.1297 


481 


4 


54 


285.7 


1201. 1 


288 


.1320 


472 


9 


55 


286.9 


1201.4 


289.2 


•1343 


464 


7 



Practical Application of the Indicator. 181 

Table 2 — Continued. 



Absolute 
pressure in 
pounds per 


Temperature 

in Fahrenheit 

degrees. 


Total heat- 
units per 
pound above 


Heat-units 

per pound 

contained in 


Weight in 

decimals of a 

pound per 


Specific 
volume. 


square inch. 


zero (32 ). 


the water. 


cubic foot. 




56 


288.1 


1201.8 


290.3 


.1366 


457 


57 


289.1 


1202. 1 


291.5 


.1388 


449.6 


53 


290.3 


1202. 5 


292.7 


. I4I I 


442.4 


59 


291.4 


1202.8 


293.8 


-I434 


435-3 


60 


292.5 


1203.2 


294.9 


•1457 


428.5 


61 


293.6 


1203.5 


296 


.1479 


422 


62 


294.7 


1203.8 


297.1 


. 1502 


415.6 


63 


295.7 


1204. 1 


298.2 


.1525 


409 


4 


64 


296.8 


1204.5 


299.2 


-I547 


403 


5 


65 


297.8 


1204.8 


300.3 


.1570 


397 


7 


66 


298.8 


1205. 1 


30I.3 


.1592 


392 


1 


67 


299.8 


1205.4 


302.4 


. l6l5 


386 


6 


68 


300.8 


1205.7 


303.4 


•1637 


38i 


3 


69 


301.8 


1206 


304.4 


. I66O 


376 


1 


70 


302.7 


1206.3 


305.4 


.1682 


37i 


2 


7i 


303.7 


1206.6 


306.4 


.1704 


366 


4 


72 


3O4.6 


1206.9 


307.3 


. 1726 


361 


7 


73 


3O5.6 


1207. 1 


308.3 


.1748 


357 


1 


74 


306.5 


1207.4 


309.3 


.1770 


352 


6 


75 


307.4 


1207.7 


310.2 


.1792 


348 


3 


76 


308.3 


1208 


311. I 


.1814 


344 


1 


77 


309.2 


1208.2 


312 


.1836 


340 


78 


3IO.I 


1208.5 


313 


.1858 


336 


79 


3IO.9 


1208.8 


313-8 


.I88O 


332.1 


80 


311,8 


1209 


314-7 


.1901 


328.3 


81 


312.7 


1209.3 


315-6 


.1923 


324.6 


82 


313-5 


1209.6 


316.5 


.1945 


320.9 


83 


3I4.4 


1209.8 


317-3 


.1967 


317.3 


84 


3I5-2 


1210 


318.2 


.1989 


313-9 


85 


3l6 


1 2 10. 3 


319 


.20IO 


310.5 



182 Practical Application of the Indicator. 

Table 2 — Continued. 



Absolute 
pressure in 
pounds per 
square inch. 


Temperature 

in Fahrenheit 

degrees. 


Total heat- 
units per 
pound above 
zero (32 ). 


Heat-units \ 

per pound de 

contained in p 

the water. c 


Veight in 
cimals of a 
ound per 
ubic foot. 


Specific 
volume. 


86 


316.8 


I 2 10. 6 


319-9 


.2032 


307.2 


87 


317.6 


I 2 10. 8 


320.7 


.2053 


304 


88 


318.5 


121 I 


321.5 


•2075 


300.8 


89 


319-3 


I2Ii:3 


322.4 


2097 


297.7 


90 


320 


I2II.6 


323-2 


2Il8 


294.7 


9i 


320.8 


I2II.8 


324 


2139 


291.8 


92 


321 


6 


1212 


324.8 


2l6l 


288.9 


93 


322 


4 


I2I2.3 


325.6 


2183 


286.1 


94 


323 


1 


1212. 5 


326.4 


2204 


283.3 


95 


323 


9 


I2I2.7 


327-1 


2225 


280.6 


96 


324 


6 


1213 


327-9 


2245 


278 


97 


325 


4 


I2I3.2 


328.7 


2267 


275-4 


98 


326 


1 


I213.4 


329-4 


2288 


272.8 


99 


326 


8 


I2I3.6 


330.2 


2 309 


270.3 


100 


327 


6 


I2I3.8 


331 


2330 


267.9 


IOI 


328 


3 


1214 


331-7 


2351 


265.5 


102 


329 




I214.3 


332.4 


2372 


263.2 


103 


329 


7 


I2I4.5 


333-1 


2392 


260.9 


104 


330 


4 


I2I4.7 


333-9 


2413 


258.7 


105 


331 


1 


I214.9 


334-6 


2434 


256.5 


106 


331 


8 


1215. I 


335-3 


2455 


2 54-3 


107 


332 


5 


1215.3 


336 


2475 


252.2 


108 


333 


2 


I2I5.6 


336.7 


•2496 


250. 1 


109 


333 


9 


I2I5.8 


337-4 


2517 


248 


1 10 


334 


5 


I2l6 


338.1 


2538 


246 


11 1 


335 


.2 


I2I6.2 


338.8 


2558 


244 


1 12 


335 


9 


I2I6.4 


339-5 


2579 


242 


113 


336 


•5 


I2I6.6 


340.2 


2599 


240. 1 


114 


337 


2 


I2I6.8 


340.8 


2620 


238.2 


115 


337 


8 


1217 


341-5 


264O 


236.3 



Practical Applicatio?i of the Indicator. 183 

Table 2 — Continued. 



Absolute 


Temperature 


Total heat- 


Heat-units V 


/eight in 




pressure in 


units per 


per pound dec 


imals of a 


Specific 


pounds per 


in p eifirenriei t 
degrees. 


pound above|contained in p 


ound ppr 


volume. 


square inch. 


zero (32 ). 


the water. c 


abic foot. 




Il6 


338.5 


I2I7.2 


342.2 


266l 


234-5 


117 


339-1 


1217 


4 


342. 


8 


2682 


232.7 


Il8 


339-7 


1217 


6 


343- 


5 


2702 


231 


119 


340.4 


1217 


8 


344 


2 


2722 


229.3 


I20 


34i 


1217 


9 


344- 


8 


2743 


227.6 


121 


341-6 


I2I8 


1 


345 


4 


2763 


226 


122 


342,2, 


I2I8 


3 


346 


1 


2783 


224.4 


123 


342.9 


I2I8 


5 


346 


7 


2803 


222.8 


124 


343-5 


I2I8 


7 


347 


3 


2823 


221.2 


125 


344-1 


I2I8 


9 


348 


2843 


219.7 


126 


344-7 


1219 


1 


348.6 


2862 


218.2 


127 


345-3 


1219 


3 


349 


2 


2882 


216.7 


128 


345-9 


1219 


4 


349 


8 


2902 


215.2 


129 


346.5 


1219 


6 


350 


4 


2922 


213-7 


I30 


347-1 


1219 


8 


35i 


1 


2942 


212.3 


131 


347-6 


1220 


35i 


7 


.2962 


210.9 


132 


348.2 


1220. 2 


352 


3 


2982 


209.5 


133 


348.8 


1220.4 


352 


9 


300I 


208. 1 


134 


349-4 


I220. 5 


353 


5 


302I 


206.7 


135 


350 


I220.7 


354 


1 


3040 


205.4 


136 


350.5 


1220.9 


354 


6 


3060 


204. 1 


137 


35i-i 


1221 


355 


2 


3080 


202.8 


138 


351-7 


I22I.2 


355 


8 


3099 


201. 5 


139 


352.2 


I22I.4 


356 


4 


3119 


200.2 


I4O 


352.8 


122 1. 5 


357 


3139 


199 


141 


353-3 


I22I.7 


357-5 


•3159 


197-8 


142 


353-9 


I22I.9 


358 


1 


.3179 


196.6 


143 


354-4 


1222 


358 


7 


.3199 


195-4 


144 


355 


1222.2 


359 


2 


.3219 


194.2 


145 


355-5 


1222.4 


359 


.8 


.3239 


193 



184 Practical Application of the Indicator. 

Table 2 — Continued. 



Absolute 
pressure in 
pounds per 
square inch. 


Temperature 

in Fahrenheit 

degrees. 


Total heat- 
units per 
pound above 
zero (32 ). 


Heat-units \ 

per pound de 

contained in p 

the water. c 


Veight in 
;imals of a 
ound per 
ubic foot. 


Specific 
volume 




I46 


356 


1222.5 


360.4 


3259 


191 


9 


147 


356.6 


1222.7 


360 


•9 


3279 


I90 


8 


I48 


357-1 


1222.9 


36l 


5 


3299 


I89 


7 


149 


357-6 


1223 


362 




3320 


188 


6 


I50 


358-1 


1223.2 


362 


.6 


3340 


187 


5 


151 


358-7 


1223.3 


363 


1 


3358 


186 


4 


152 


359-2 


1223.5 


363 


6 


3376 


I85 


3 


153 


359-7 


1223.7 


364 


2 


3394 


I84 


3 


154 


360.2 


1223.9 


364 


7 


3412 


183 


3 


155 


360.7 


1224 


365 


2 


3430 


182 


3 


I 5 6 


361.2 


1224. I 


365 


8 


3448 


l8l 


3 


157 


361.8 


1224.3 


366 


3 


3467 


180 


3 


I 5 8 


362.3 


I324.4 


366 


8 


3485 


179 


3 


159 


362.8 


1224.6 


367 


3 


3503 


178. 


3 


l60 


363.3 


1224.8 


367 


9 


352i 


177 


3 


l6l 


363.8 


1224.9 


368 


4 


3540 


I76. 


4 


l62 


364-3 


1225 


368 


9 


3558 


175- 


5 


163 


364.8 


1225.2 


369 


4 


3577 


174 


6 


164 


365.2 


1225.3 


369 


9 


3596 


173- 


7 


I6 5 


365.7 


1225.5 


370 


4 


3615 


172. 


8 


166 


366.2 


1225.6 


370 


9 


3634 


171 


9 


167 


366.7 


1225.8 


371 


4 


3652 


171 




168 


367.2 


1225.9 


371 


9 


•3671 


170. 


1 


I69 


367-7 


1226. I 


372 


4 


3690 


169. 


2 


I/O 


368.2 


1226.2 


372 


9 


3709 


168. 


4 


171 


368.6 


1226.4 


373 


4 


3727 


167. 


6 


172 


369.1 


1226. 5 


373 


9 


3745 


166. 


8 


173 


369.6 


1226.7 


374 


4 


3763 


166 




174 


37o 


1226.8 


374 


9 


378i 


165. 


2 


175 


37o.5 


1226.9 


375 


4 


3799 


164. 


4 



Practical Application of the Indicator. 185 

Table 2 — Concluded. 



Absolute 
pressure in 
pounds per 
square inch. 


Temperature 

in Fahrenheit 

degrees. 


Total heat- 
units per 
pound above 
zero (32 ). 


Heat-units V 

per pound de 

contained in p 

the water. c 


height in 
:imals of a 
ound per 
ubic foot. 


Specific 
volume. 


176 


371 


1227. I 


375-9 


3817 


163.6 


177 


371-4 


1227.2 


376 


3 


3835 


162.8 


178 


371.9 


1227.4 


376 


8 


3853 


l62 


179 


372.4 


1227. 5 


377 


3 


3871 


l6l. 2 


I8O 


372.8 


1227.7 


377 


8 


3889 


160.4 


l8l 


373-3 


1227.8 


378 


3 


3908 


159.7 


182 


373-7 


1227.9 


378 


7 


3926 


159 


183 


374-2 


1228. I 


379 


2 


3944 


158.3 


I84 


374-6 


1228.2 


379 


7 


3962 


157.6 


I8 5 


375-1 


1228.3 


380 


1 


398i 


156.9 


186 


375-5 


1228.5 


380 


6 


3999 


156.2 


I87 


376 


1228.6 


381 


1 


4017 


155-5 


I88 


376.4 


1228.7 


38i 


5 


4036 


154.8 


I89 


376.9 


1228.9 


382 




4054 


154. I 


I90 


377-3 


1229 


382 


4 


4072 


153-4 


191 


377-7 


1229. I 


382 


9 


.4090 


152.7 


192 


378.2 


1229.3 


383 


3 


4108 


152 


193 


378.6 


1229.4 


383 


8 


4125 


i5i-3 


194 


379 


1229. 5 


384 


2 


4143 


150.7 


195 


379-5 


1229.7 


384 


7 


4160 


150. 1 


I96 


380 


1229.8 


385 


1 


4178 


149.5 


197 


380.3 


1229.9 


385 


6 


4196 


148.9 


198 


380.7 


I230. I 


386 




4214 


148.3 


199 


381. 1 


I230.2 


386 


5 


4232 


147-7 


200 


381.6 


I230.3 


386. 


9 


4250 


147. 1 



186 



.Practical Application of the Indicator, 



Table 3. 
one-half area of circles in square inches. 



Diameter 
in inches. 


One-half 

area in 

square ins. 


Diameter 
in inches. 


One-half 

area in 

square ins. 


Diameter 
in inches. 


One-half 

area in 

square ins. 


0- 




2- 


I.5708 


4— 


6.283 


1-16 


.OOI5 


I-16 


I.669O 


1-16 


6.48I 


1-8 


.006l 


1-8 


1.7732 


1-8 


6.682 


3-16 


.OI38 


3-16 


1.8792 


3-16 


6.886 


i-4 


.0245 


1-4 


I.988O 


i-4 


7.093 


5-16 


.0383 


5-16 


2. IOOO 


5-16 


7.303 


3-8 


.0552 


3-8 


2.2I5I 


3-8 


7.516 


7-16 


.7516 


7-16 


2-3533 


7-16 


7-732 


1-2 


.9817 


1-2 


2-4543 


1-2 


7-952 


9-16 


•1242 


9-16 


2.5786 


9-16 


8.174 


5-8 


•1534 


5-8 


3.7059 


5-8 


8.400 


1 1-16 


.I856 


1 1-16 


2.8361 


11-16 


8.628 


3-4 


.2208 


3-4 


2.9697 


3-4 


8.860 


13-16 


.2592 


13-16 


3.IO63 


13-16 


9.095 


7-8 


.3OO6 


7-8 


3-2459 


7-8 


9-332 


15-16 


.3451 


15-16 


3-3886 


15-16 


9-573 


1 — 


•3927 


3- 


3-5343 


5- 


9.817 


1-16 


•4433 


1-16 


3-6831 


1-16 


10.064 


1-8 


.4970 


1-8 


3-8349 


1-8 


10.314 


3-16 


•5537 


3-16 


3.9899 


3-16 


10. 567 


i-4 


•6135 


1-4 


4.1478 


i-4 


10.823 


5-16 


.6765 


5-16 


4.3090 


5-16 


11.083 


3-8 


.7424 


3-8 


4-4731 


3-8 


H-345 


7-16 


.8114 


7-16 


4.6403 


7-16 


1 1. 610 


1-2 


.8835 


1-2 


4.8105 


1-2 


11.879 


9-16 


.9587 


9-16 


4.9840 


9-16 


12. 150 


5-8 


1.0369 


5-8 


5. 160 


5-8 


12.425 


1 1-16 


1.1182 


1 1-16 


5-339 


11-16 


12.703 


3-4 


1.2026 


3-4 


5.522 


3-4 


12.983 


13-16 


1.2900 


13-16 


5.708 


13-16 


13.267 


7-8 


1.3805 


7-8 


5.896 


7-8 


13-554 


15-16 


1. 4741 


15-16 


6.088 


15-16 


13-844 



Practical Application of the Indicator. 



187 



Table 4. 
area of circles in square inches. 



Diameter 


Area in 


Diameter 


Area in 


Diameter 


Area in 


in inches. 


square ins. 


in inches. 


square ins. 


in inches. 


square ins. 


O. 




8. 


50.265 


16. 


20I.06 





25 


.O49O 


8. 


25 


53 


456 


l6.25 


207.39 





5 




1963 


8. 


5 


56 


745 


16.5 


213.82 





75 




4417 


8. 


75 


60 


132 


16.75 


220.35 


I 






7854 


9. 




63 


617 


17- 


226.98 


I 


25 


I 


227 


9- 


25 


67 


200 


17.25 


233-70 


I 


5 


I 


767 


9- 


5 


70 


882 


17-5 


24O. 52 


I 


75 


2 


405 


9 


75 


74 


662 


17-75 


247-45 


2 




3 


141 


10 




78 


540 


18. 


254.46 


2 


25 


3 


976 


10 


25 


82 


516 


18.25 


261.58 


2 


5 


4 


908 


10 


5 


86 


590 


18.5 


268.80 


2 


75 


5 


•939 


10 


75 


90 


762 


18.75 


276. I I 


3 




7 


068 


11 




95 


o33 


19. 


283.52 


3 


25 


8 


295 


1 1 


25 


99 


402 


19.25 


29I.03 


3 


5 


9 


621 


1 1 


5 


103 


86 


19.5 


298.64 


3 


75 


1 1 


044 


11 


75 


108 


43 


19-75 


306.35 


4 




12 


566 


12 




113 


09 


20. 


3I4.I6 


4 


25 


14 


186 


12 


25 


117 


85 


20.25 


322.06 


4 


5 


15 


904 


12 


5 


122 


7i 


20.5 


330.06 


4 


75 


17 


720 


12 


75 


127 


67 


20.75 


338.16 


5 




19 


635 


13 




132 


73 


21. 


346.36 


5 


•25 


21 


647 


13 


25 


137 


88 


• 21.25 


354-65 


5 


5 


23 


758 


13 


5 


143 


13 


21.5 


363-05 


5 


•75 


25 


967 


13 


75 


148 


48 


21.75 


371-54 


6 




28 


274 


14 




153 


93 


22. 


380.13 


6 


•25 


30 


679 


14 


25 


159 


48 


22.25 


388.82 


6 


•5 


33 


183 


14 


•5 


165 


•13 


22. 5 


397.60 


6 


•75 


35 


784 


14 


75 


170 


•87 


22.75 


406.49 


7 




38 


484 


15 




176 


7i 


23- 


4I5-47 


7 


•25 


4i 


.282 


15 


25 


182 


.65 


23.25 


424-55 


7-5 


44 


178 


15 


5 


188 


.69 


23-5 


433-73 


7-75 


47 


173 


15 


75 


194.82 


23-75 


443-OI 



188 Practical Application of the Indicator. 

Table 4 — Concluded. 



Diameter 


Area in 


Diameter 


Area in 


Diameter 


Area in 


in inches. 


square ins. 


in inches. 


square ins. 


in inches. 


square ins. 


24. 


452.39 


32. 


8O4.24 


40. 


1256.6 


24 


25 


461.86 


32 


25 


8l6.86 


40 


25 


1272.3 


24 


5 


471-43 


32 


5 


829.57 


40 


5 


1288.2 


24 


75 


481.10 


32 


75 


842.39 


40 


75 


1304.2 


2 5 




490.87 


33 




855-30 


41 




1320.2 


2 5 


25 


500. 74 


33 


25 


868.3O 


41 


25 


1336.4 


25 


5 


510.70 


33 


5 


88I.4I 


41 


5 


1352.6 


25 


75 


520.76 


33 


75 


894.61 


41 


75 


I369.O 


26 




530.93 


34 




9O7.92 


42 




I385-4 


26 


25 


541.18 


34 


25 


921.32 


42 


25 


1 40 1 . 9 


26 


5 


551-54 


34 


5 


934.82 


42 


5 


1418.6 


26 


75 


562.00 


34 


75 


948.41 


42 


75 


1435-3 


27 




572.55 


35 




962. I I 


43 




1452.2 


27 


25 


583.20 


35 


25 


975.90 


43 


25 


1469. 1 


27 


5 


593-95 


35 


5 


989.8O 


43 


5 


i486. 1 


27 


75 


604. 80 


35 


75 


IOO3.7 


43 


75 


I503-3 


28 




615.75 


36 




IOI7.8 


44 




1520.5 


28 


25 


626. 79 


36 


25 


1032.0 


44 


25 


1537-8 


28 


5 


637-94 


36 


5 


IO46.3 


44 


5 


1555-2 


28 


75 


649.18 


36 


75 


IO60.7 


44 


75 


1572.8 


29 




660.52 


37 




1075.2 


45 




1590.4 


29 


25 


671.95 


37 


25 


IO89.7 


45 


25 


1608. 1 


29 


5 


683.49 


37 


5 


I IO4.4 


45 


5 


1625.9 


29 


75 


695.12 


37 


75 


II 19. 2 


45 


75 


1643-8 


30 




706. 86 


38 




I I 34. I 


46 




1 66 1. 9 


30 


25 


718.69 


38 


25 


I I49.O 


46 


25 


1680.0 


3O 


5 


730.61 


38 


•5 


I 164. 1 


46 


5 


1698.2 


30 


75 


742.64 


38 


75 


H79-3 


46 


75 


1716.5 


31 




754.76 


39 




1 194. 5 


47 




1734-9 


31 


25 


766.99 


39 


25 


1209.9 


47 


25 


1753-4 


31.5 


779-31 


39 


5 


1225.4 


47 


5 


1772.0 


31.75 


791-73 


39 


75 


1240.9 


47 


75 


1790.7 



CHAPTER XVI. 

ANALYSIS OF DIAGRAM FROM AMMONIA COMPRESSOR. 

Fig. 88 shows the general features of a well formed 
diagram from an ammonia compressor, the attainment 
of which should be the aim in running an ammonia 
machine. The following names have been given to 
the different parts of the diagram for the purpose of 




Fig. 88— Scale of Spring 80 

analysis, and it will be seen that the transactions 
taking place in forming this diagram are vice versa to 
those taking place in forming the diagram from a 
steam engine cylinder, or in other words an ammonia 
compressor is simply a pump. The line AA is the 
atmospheric line and is taken after the ammonia is 
shut off from the indicator. The line BC is the suc- 
tion line and represents by its distance above the 

189 



190 Practical Application of the Indicator, 

atmospheric line the suction pressure in the com- 
pressor at any point in the stroke and there should 
not be a greater loss of pressure than is required to 
raise the suction valves and the minimum friction in 
the passages, as this is a corresponding loss of duty 
and capacity. The indicated suction pressure which 
is measured on the scale of the spring from the atmos- 
pheric line to the suction line, when deducted from 
the suction pressure by gauge, gives the loss of pres- 
sure through the passages. When the piston has 
completed its stroke as shown at the point C the suc- 
tion valves close and the ammonia gas is imprisoned 
and as the piston is returning the pressure rises and 
forms the compression curve C D as shown by the 
arrow and according to Mariotte's law \ 'a perfect gas is 
inversely proportional to its volume," and assuming 
that ammonia gas is a perfect gas and that the pres- 
sure at the end of the stroke is 20 pounds absolute 
which is the atmospheric pressure plus the pressure 
above the atmospheric and at one-half stroke (clear- 
ance neglected) the volume is one-half and the pres- 
sure is doubled or 40 pounds, and at three-quarter 
stroke the volume is again one-half of that at one-half 
stroke and the pressure is again doubled or 80 pounds 
absolute and so on. But should the absolute pressure 
at one-half stroke plus one-half the clearance be 
greater than double the absolute pressure at the com- 
mencement of the return stroke it indicates leakage 
into the compressor through the discharge valves; and 
if less, leakage out of the compressor through the suc- 
tion valves or piston, or both. But, however, the leak- 
age into and out of the compressor may balance each 



Practical Application of the Indicator. 191 

other and would indicate no leakage, therefore this 
test should be made on the machine itself and under 
the actual pressure. 

When the compressing pressure exceeds the con- 
densing pressure as shown at the point D, the discharge 
valves open and form the discharge line DE; the dis- 
charge pressure is measured on the scale of the spring 
from the atmospheric line to the discharge line and 
the indicated discharge pressure should not exceed 
the condensing pressure more than is required to raise 
the discharge valves, and the minimum friction in the 
passages, as this loss in pressure is another loss in 
duty and capacity. And supposing the indicated dis- 
charge pressure is 145 pounds and the condensing 
pressure by gauge is 140 pounds, it shows a loss of 5 
pounds. Should there be a serious loss in the suction 
and discharge pressures the speed of the machine is 
beyond the capacity of the passages, a matter which 
can be tested by varying the speed. 

The line EB is the release pressure line, and if 
there is no leakage into the clearance space through 
the discharge valve and the clearance is small, this 
line should fall nearly perpendicular and at right angles 
to the atmospheric line but when there is a leak into 
the clearance space or excessive clearance, this line 
forms a curve by curving inward and is another loss. 

Such parts of the indicator as come in contact 
with the ammonia gas must be constructed of steel as 
the steam engine indicator being made of brass will 
not withstand the action of the ammonia gas. 

In attaching the indicator the same precautions 
must be taken as on a steam engine cylinder. 



192 Practical Application of the Indicator. 

DIAGRAMS FROM AMMONIA COMPRESSOR SHOWING LEAKS 
AND OTHER DEFECTS. 

Fig. 89 shows a diagram from a I4"X28" Am- 
monia Compressor, revolutions 50; suction and dis- 
charge pressure respectively 11 and 160 pounds by 
gauge. 

The suction pressure measures 6 pounds and shows 
a loss of 5 pounds in the suction passages. The dis- 
charge pressure measures 150 pounds and shows a 



Fig. 89— Scale of Spring 100 

loss of 10 pounds in the discharge passages. It is 
evident the speed of the machine was beyond the ca- 
pacity of the passages and did not allow a free passage 
for the ammonia gas. 

In determining the loss of pressure as in all similar 
tests, the indicator and gauges should be compared 
according to the explanations given on pages 30, 31 
and 32. The discharge line is wavy and is caused by 
a fluctuation in the pressure. When more than one 
machine js discharging into the condensor, it frequently 
causes abrupt irregularities at different points in the 
discharge line. 



Practical Application of the Indicator. 



193 



The release pressure line curves greatly inward 
and the pressure is not reduced to the suction pressure 
until the piston has moved a distance proportionate 
to the length of the dotted line, which measures . 76 
inches, divided by the length of the diagram, 3 inches, 
shows 25 J per cent, loss of pumping capacity in the 
compressor, due to the expansion of the clearance- 
space gas, providing there was no leakage. But in 




Fig. 90— Scale of Spring 80. 



this case the discharge valve leaked and prolonged 
the curve and followed with a too rapid rising in the 
compression curve. And since this leakage is taking 
place throughout the entire revolution except during 
the time of discharge, it results in a still greater loss 
in capacity. 

Fig. 90 shows another diagram representing leaks 

and is taken from a 14/X24" Ammonia Compressor. 

Revolutions, 40. The release pressure line as shown 

at the right hand end of this diagram also curves 

13 



194 Practical Application of the Indicator. 

greatly inward and would indicate excessive clearance 
providing there was no leakage into the compressor. 
This can readily be determined on the diagram. First 
locate the vacuum line on the scale of the spring at 
such a distance below the atmospheric line as to rep- 
resent the atmospheric pressure at the time and place 
which at sea level averages about 14.7 pounds. The 
lower line is the vacuum line and the line between it 
and the suction line is the atmospheric line. Then 
from the vacuum line locate an ordinate at about a 
point on the release pressure curve as shown by the 
first dotted ordinate at the left. Next locate another 
ordinate at such a point that its height is double the 
height of the first ordinate as shown by the second 
dotted ordinate and the distance between these ordi- 
nates is the distance the clearance line should be 
located from the second ordinate, and represents by 
its distance between it and the end of the diagram, 
the percentage of clearance as compared with the 
length of the diagram. This distance is .19 of an 
inch, divided by the length of the diagram 2.90 inches 
gives 6g per cent. Example, . 19" -4- 2.90" = .o6|. 
The percentage of clearance multiplied by the stroke 
in inches gives 1.57 inches and is the clearance in 
inches as compared with the stroke in inches. Ex- 
ample, .06^X24" = 1.57". This represents a greater 
clearance than is contained in the machine and de- 
notes a leakage into the compressor through the dis- 
charge valves. Were the clearance less than is 
contained in the machine it denotes a leakage out of 
the compressor through the suction valves, piston, or 
both. 



Practical Application of the Indicator. 195 

This demonstration can also be applied to the 
compression curve of a diagram from a steam engine 
cylinder. 

To determine the leakage from the compression 
curve, which in a diagram from a steam engine 
cylinder would be the expansion curve, the demon- 
stration given in Fig. 84 may be applied, in which 
case if the pressure at the ordinate at the left is 
greater than double the pressure at the ordinate at 
the right it indicates leakage into the compressor, 
and, if less, leakage out of the compressor. When 
the theoretical curve is applied the leakage will also 
be vice versa to that shown in a diagram from a 
steam engine cylinder. 



INDEX 



PAGES. 

Preface 5, 6 

Introduction 7, 8 

The Indicator 9, 12 

Paper ..' 12, 13 

Pencil 13, 14 

Springs 14 

Application of the Indicator 15, 16 

Reducing Motion. 17, 25 

Cord 26, 28 

How to Attach the Indicator and take Diagrams ........... 28, 30 

Testing Steam Gauge with the Indicator 30, 32 

Diagram Analysis 33, 40 

Cushion 41, 47 

Corliss Engine: — Diagrams from Corliss Condensing Engine. 48, 51 

Setting Corliss Valves with the Indicator 52, 68 

Diagram from Steam Pipe 69, 70 

Eccentric too late 71, 72 

Diagrams from the same Engine before and after adjust- 
ing with the Indicator 73, 77 

Good adjustments by a novice with the Indicator 77, 80 

Diagrams showing different effects in Cushion with and 

without the Condenser. . . 80, 83 

Diagrams from overloaded Corliss Condensing Engines. . . 83, 90 

Diagrams showing Leaky Exhaust Valves 90, 93 

A distorted diagram caused by imperfect reducing motion 93, 95 
Diagram from a modern Corliss Engine showing faulty 

construction.. 96, 97 

Riding Cut-off Engine: — Setting automatic Riding cut-off 

Valves with the Indicator 98, 107 

Diagrams from an Engine on which an Indica'or had 

not been used for eleven years 107, no 

Diagrams showing incorrect adjustments no, n 1 

Setting automatic Riding cut-off valves by the sound of 

the exhaust 112, 113 

iq6 



Index. 197 

Single Valve Engine: — Setting single valve automatics 

with the Indicator 114, 119 

An excellent diagram from a modern high-speed Engine 120, 121 
A diagram from a modern high-speed Engine, showing 

faulty construction ; 121, 124 

Setting single valve automatics by the sound of the ex- 
haust, 124, 126 

A distorted diagram caused by insufficient tension of the 

drum-spring 127, 128 

Diagrams from an overloaded high-speed Engine 129, 130 

Diagrams from each end of the cylinder, showing a 

difference in the initial pressure 130, 131 

Serrated curves caused by unequal expansion of the 

Indicator-Piston and Cylinder 131, 132 

Throttling or slide valve Engine 132, 134 

Typical compression curves and admission lines 134, 136 

Defective steam lines 136, 138 

Pumps: — Analysis of boiler feed pump diagrams 139, 142 

Diagrams from boiler feed pump showing leakage in 

the discharge passages 142, 145 

Diagram showing absence of elastic cushion causing 

irregularities in the discharge line. 145 

Peculiar compression and release pressure lines 146, 149 

Mean Effective Pressure: — Calculating the mean effective 

pressure by ordinates 150, 155 

The Planimeter 156 

Calculating the mean effective pressure with the Planimeter 156, 162 

To compute the Indicated Horse Power of an Engine 163, 166 

Testing the valves and piston for leaks 167, 168 

To ascertain the percentage of clearance in an Engine 168, 169 

Method of locating the clearance line and determining leak- 
age on the diagram 169, 171 

Locating the theoretical curve 172, 173 

Locating the theoretical point of cut-off ... - 173, 174 

Computing the water consumption per Indicated Horse 

Power per hour from the diagrams 174, 177 

Tables: — Temperature of Vacuum 178 

Properties of saturated steam 1 79, 185 

One-half area of circles 168 

Area of circles 187, 188 

Ammonia: — Analysis of diagram from ammonia compressor 189, 191 
Diagrams from ammonia compressor showing leaks and 

other defects 192, 195 



.. Announcement .. 



r I "HE author now has his office at 25 West 
* Lake Street, where he will be pleased to re- 
ceive professional calls, and to which place all cor- 
respondence may be addressed. 



•**^*/N^W*/W\/S/V , \A'S*/V\/W^«A/VVV\A 



Duty and Capacity Tests of Steamship, Locomotive 
and Stationary Engines, Boilers, Pumps, etc. 

Steam and Gas Engines, Ammonia and Air Com- 
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HIGHEST REFERENCES. 



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Consulting Engineer 

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